Some great points here, and i'll join the 'I'm in it for the Single Player mostly' crowd 
Here is a nice topic looking at the theoretical but distinctly real option of a 'warp-drive':
http://www.gizmag.com/warp-drive-bubble-nasa-interstellar/24392/
=======================================
[Note: This may be a huge post!]
Now lets look at the main conflict between the different Elite's and elite players. Combat:
Elite: didn't use Newtonian-physics and had earth/atmosphere based like dog-fighting in space.
Plus = the combat was often intense and fitted in with our frames of reference due to the historic link to aerial battles.
Minus = missed out on lots of space flight based stuff around gravity effects etc.
Frontier: Newtonian-physics and the combat nearly always became a 'space-joust' with 1 enemy at a time (sometimes more).
FFE: As above, but i found combat to be more likely to involve more than one ship at a time, less 'space joust' and more like in the original. I didn' come to FFE until a few years ago, so it had been all patched etc by that point.
Both having Newtonian-physics made space in general more interesting, and while the 'space-joust' combat of Frontier was not hugely fun, that seemed 'fixed' in FFE so both situations, Newtonian-physics AND more dog-fighting could exist side by side. So i hope we see something more like what we ended up with in FFE. I've played FFE over the last few days, just to be sure i was correct on this, and yes in FFE you can get into multi-ship dog fights, which were rare in Frontier. It is not quite the same as the dogfights in Elite (and earth based flight-sims), but it is a step in the right direction.
=================
Back to the single-player aspirations of Elite: Dangerous.
1. Space Flight: Carry on where the other games (Elite, Frontier, Frontier First Encounters) left off, in terms of ambition and simulation of space travel.
For space travel i'd have no issue seeing something like that 'warp bubble' manipulated to fit into the game so it would enable part of the function of what the 'Star-Dreamer' could achieve in the Frontier and FFE games.
If we have some kind of Elite-like 'Hyper-drive' for travel between systems, that is cool. And for in-system travel using a warp-bubble to speed up travel between points could work, without the need to adjust time outside of the bubble. I'm not too distressed if science has to be slightly adjusted to fit reasonable gameplay on this.
What i liked about the 'Star Dreamer' was that it made traveling 'real world' distances in space possible. What i didn't like about it was the suspension of disbelief in how time was (in effect) sped up for the whole universe.
Once i had jumped into a system i used it in a step-method, as this gave me the greatest appreciation of the beauty of space travel. So at first i would speed up time to maximum until i was about 10-15AU out, then i would slow down to half maximum until i was about 6AU out, then a quarter maximum from 3AU out etc (once combats were done). This made approaching the planet or space station a real pleasure to enjoy, while not taking up so much time but also not letting it all whiz by in a blur i could not appreciate.
So I would hope for some form of in-system travel that is fast enough, but not too fast, to ensure that feeling and wonder of space travel is retained.
2. Trade: Expand the economic system. There are many examples we could use (from the 'X' games to others) to include a wider array of trade goods in the game, and a real way to enact any penalty for ferrying certain forbidden items. I think all the Elite's added layers to this but it never felt 'fully' finished even in FFE. Have police Vipers that can scan your ship, have customs at star-ports that investigate your ship and business (you can make all the dialogues much more like they are in real life for this etc). Trade and crime can be fitted together to make you really feel the danger of being a smuggler or pirate, as opposed to the slightly hit or miss result Elite achieved so far.
Missions will be important in this also, the bullitin-boards of Frontier and FFE were a great way to get random generic content for the player to interact with, and i think that can be added to and improved upon quite a bit to really bring the feeling of a thriving, wheeling and dealing galaxy to life. Different tax rates, different goods related to different planets (some unique goods even), player owned property etc, there is so much that could be done here.
3. Factions: These were great fun in Frontier and FFE, so i hope they are expanded upon. From the military side to a more 'political' aspect maybe? They are certainly a strong contender for helping create the games atmosphere and background, and they just scratched the surface in the previous Elites imho.
I can go on with loads of things, but time is against me!
=============================
The bottom line: For me the single player aspect has to be a priority, otherwise it is not really 'Elite' so much as an 'Elite-like'. And i would say to do a successful single player Elite: Dangerous, you need to take what the series has achieved upto this point and carry on to do the natural progression and expansion of that.
To be the successes it can be, Elite: Dangerous should not loose sight of where it has come from and the why of that. IF it simply goes chasing the pot of gold that most publishers are so obsessed with, it will simply be another flash-in-the-pan that most likely won't be long lived or long remembered, other than for it's infamy (of failing to adhere to it's roots).
We players are not simply cash-cows, and if treated as such often don't respond well, especially not in the area of PC gaming Elite is at home in, we are not facebook-game players (for the most part) nor 'casual' gamers with short attention spans etc.
Chris Roberts got nearly 100,000 people to put up money for a game they won't see for 2 years. Those are the risk-taking early adopters, the smaller percentage of people that will likely end up buying the game when it is finished. There is no reason Elite: Dangerous can not do the same.
Here is a nice topic looking at the theoretical but distinctly real option of a 'warp-drive':
http://www.gizmag.com/warp-drive-bubble-nasa-interstellar/24392/
=======================================
[Note: This may be a huge post!]
Now lets look at the main conflict between the different Elite's and elite players. Combat:
Elite: didn't use Newtonian-physics and had earth/atmosphere based like dog-fighting in space.
Plus = the combat was often intense and fitted in with our frames of reference due to the historic link to aerial battles.
Minus = missed out on lots of space flight based stuff around gravity effects etc.
Frontier: Newtonian-physics and the combat nearly always became a 'space-joust' with 1 enemy at a time (sometimes more).
FFE: As above, but i found combat to be more likely to involve more than one ship at a time, less 'space joust' and more like in the original. I didn' come to FFE until a few years ago, so it had been all patched etc by that point.
Both having Newtonian-physics made space in general more interesting, and while the 'space-joust' combat of Frontier was not hugely fun, that seemed 'fixed' in FFE so both situations, Newtonian-physics AND more dog-fighting could exist side by side. So i hope we see something more like what we ended up with in FFE. I've played FFE over the last few days, just to be sure i was correct on this, and yes in FFE you can get into multi-ship dog fights, which were rare in Frontier. It is not quite the same as the dogfights in Elite (and earth based flight-sims), but it is a step in the right direction.
=================
Back to the single-player aspirations of Elite: Dangerous.
1. Space Flight: Carry on where the other games (Elite, Frontier, Frontier First Encounters) left off, in terms of ambition and simulation of space travel.
For space travel i'd have no issue seeing something like that 'warp bubble' manipulated to fit into the game so it would enable part of the function of what the 'Star-Dreamer' could achieve in the Frontier and FFE games.
If we have some kind of Elite-like 'Hyper-drive' for travel between systems, that is cool. And for in-system travel using a warp-bubble to speed up travel between points could work, without the need to adjust time outside of the bubble. I'm not too distressed if science has to be slightly adjusted to fit reasonable gameplay on this.
What i liked about the 'Star Dreamer' was that it made traveling 'real world' distances in space possible. What i didn't like about it was the suspension of disbelief in how time was (in effect) sped up for the whole universe.
Once i had jumped into a system i used it in a step-method, as this gave me the greatest appreciation of the beauty of space travel. So at first i would speed up time to maximum until i was about 10-15AU out, then i would slow down to half maximum until i was about 6AU out, then a quarter maximum from 3AU out etc (once combats were done). This made approaching the planet or space station a real pleasure to enjoy, while not taking up so much time but also not letting it all whiz by in a blur i could not appreciate.
So I would hope for some form of in-system travel that is fast enough, but not too fast, to ensure that feeling and wonder of space travel is retained.
2. Trade: Expand the economic system. There are many examples we could use (from the 'X' games to others) to include a wider array of trade goods in the game, and a real way to enact any penalty for ferrying certain forbidden items. I think all the Elite's added layers to this but it never felt 'fully' finished even in FFE. Have police Vipers that can scan your ship, have customs at star-ports that investigate your ship and business (you can make all the dialogues much more like they are in real life for this etc). Trade and crime can be fitted together to make you really feel the danger of being a smuggler or pirate, as opposed to the slightly hit or miss result Elite achieved so far.
Missions will be important in this also, the bullitin-boards of Frontier and FFE were a great way to get random generic content for the player to interact with, and i think that can be added to and improved upon quite a bit to really bring the feeling of a thriving, wheeling and dealing galaxy to life. Different tax rates, different goods related to different planets (some unique goods even), player owned property etc, there is so much that could be done here.
3. Factions: These were great fun in Frontier and FFE, so i hope they are expanded upon. From the military side to a more 'political' aspect maybe? They are certainly a strong contender for helping create the games atmosphere and background, and they just scratched the surface in the previous Elites imho.
I can go on with loads of things, but time is against me!
=============================
The bottom line: For me the single player aspect has to be a priority, otherwise it is not really 'Elite' so much as an 'Elite-like'. And i would say to do a successful single player Elite: Dangerous, you need to take what the series has achieved upto this point and carry on to do the natural progression and expansion of that.
To be the successes it can be, Elite: Dangerous should not loose sight of where it has come from and the why of that. IF it simply goes chasing the pot of gold that most publishers are so obsessed with, it will simply be another flash-in-the-pan that most likely won't be long lived or long remembered, other than for it's infamy (of failing to adhere to it's roots).
We players are not simply cash-cows, and if treated as such often don't respond well, especially not in the area of PC gaming Elite is at home in, we are not facebook-game players (for the most part) nor 'casual' gamers with short attention spans etc.
Chris Roberts got nearly 100,000 people to put up money for a game they won't see for 2 years. Those are the risk-taking early adopters, the smaller percentage of people that will likely end up buying the game when it is finished. There is no reason Elite: Dangerous can not do the same.