What you think makes sense, might not make sense to FD.
As an outsider it is impossible to judge. We do not have the information.
I think developing a large project like this might be a bit more complicated than many people seem to think.
Nice job "apologizing for/spinning" FD's decisions regarding this topic. Don't know where this overwhelming urge to defend a company one has no direct connection with outside of purchasing their game comes from.

Whatever the motivation, such efforts to stifle constructive criticism only serves to muddy the waters and obstruct legitimate efforts by others in the community for timely fixes, improvements and any other actions that would lead towards a better gaming experience. Ignoring obvious flaws in the game's current design and feature list makes you either a tool for the status quo, blind, or both!
Despite literally decades of personal video game involvement, I still to this day can not understand the fanboy/apologist mindset. I have some theories including the good ol "Stockholm Syndrome", but I generally try to keep as much distance between myself and known fanboys in any video game community. About the only interesting fact I have ever gleaned from "discussions" with these "Game Developer Groupies" is that they are members of a "mono culture" who speak with one voice and regardless of the game or the development house in question, their agendas are always the same. "The developer is GOD". "Don't rock the boat". And whatever you do! "Don't Make Waves", because neither we nor the developer knows how to swim!
Now as far as what would go into a more fully fleshed out SRV feature set...
I can't imagine that creating some SRV variants would require anywhere close to the same amount of time and resources as creating an entirely new tier on top of the core game. The backend mechanics are already in the game in the form of the shipyard and outfitting sections. These could be cloned and modified to handle SRV vehicles instead of ships. The structure of both would work perfectly fine for a different collection of vehicles.
Cloning and reusing existing code is video game design 101. You are failing to take this into consideration with your estimates of resource requirement overhead for an SRV expansion project. Do you have any personal industry experience? Or are you simply a gamer with interest in the game design process?
My industry involvement spans nearly 4 DECADES. I'm not a developer, but I have managed projects. I've been a part of dozens of beta test projects both in front of and behind the table. As a paid tester as well as in some of the new public style beta test programs. I was also a projects manager at a professional audio hardware company for one of those decades. While not the same market obviously, a no less fluid and unpredictable industry with development goals, product demand and trends always coming in the form of moving targets. I do have some experience with product development, planning and development team management. Enough to contribute an "informed" opinion to this discussion.
Video game design is not rocket science. It most certainly is not the mysterious netherworld full of unknowns that you seem to think it is.

Its a creative media business just like the hundreds of others out there in the consumer and professional markets.
Frontier's decision to back burner continued development of the 2.0 core feature base was
a choice their upper management made. There is a growing body of evidence indicating that their choice was the wrong one to make. Unless you consider all the bad/negative press the 2.1 update has garnered thus far to be a good thing? All this not so flattering commentary from the game press, combined with a similar reaction from a large percentage of their fanbase. A good thing?
Here is some insight I recently learned about. Take it or leave it, as I can't disclose my source. Especially on this forum.

But since the product in question has been released and is now in the public domain, there is certainly no legal issues involved at this point...
Here we go...
I have it from a reliable source with whom I trust when it comes to such things, that what we were given within the 2.1 update was Engineers REDEUX. The original project was abandoned as it neared release due to "irreconcilable" difficulties with the projects core assets. Problems that the FD development team was simply not able and/or willing to bring under control. I pressed my source for more specifics but they were not in a position to go into more detail.
Anyway... As this story apparently goes... The decision was made to scrap the entire Engineers project as it stood at that point in time and begin development again from scratch. (Apparently, such radical moves are not uncommon when it comes to Frontier and new projects) I assume that at least some portion of the original was used in the second such as graphics and sound effects assets etc. This radical decision was the reason why the "original" 2.1 release was suddenly and unexpectedly cancelled and then delayed 3 months. This also explains why despite ALL the 2.1 development time, the Engineers product FD actually delivered to the community felt unfinished and half baked. In defense of FD's development team... Round 2 was still in very early development when marketing pressures forced FD to release 2.1 on May 26th.
We were witnessing "Seat of Your Pants" game development taken to an entirely new level! lol!
While I don't have a crystal ball and can't predict the future, I think the smart money is on the high probability that the Engineers update will be looked upon as a failure in your "10 Year Plan".
I can't help but cringe when I read any mention of it! In an industry as fast moving and unpredictable as this one, any company or project manager claiming to have a clue as to where this industry will be in 10 years and thus be able to successfully plan out a game's development course beyond the next 12-18 months is being incredibly optimistic.
