Surely you can do this already in game. You don't need an autopilot. You can point your ship at the destination and then catch up on galnet anyway, or are you talking about hyperjumping in autopilot? If so does that include fuel scooping as well? If so with the new update to the galaxy map, you can plot your route of 10,000ly keep your computer on while at work, come back and you will be at your destination.
But surely you will want to scan the systems on the way, so does the autopilot do that? If so, what about scanning interesting planets, does it do that too. I mean what exactly is the point of an autopilot except it to be a quick travel/money making system when you are not actually in front of the computer or playing the game.
I am trying to understand what people want here, as to me, it's just no making any sense at the moment.
I already adressed most of the questions you pose in the OP, such as what it should be capable of.
Furthermore, no, it's not supposed to turn this game into a farming simulator. I can see arguments for or against having one that does extra stuff, but for myself, ALL I'm interested in is automating hyperjumping, as that is the single most menial part about navigating in this game. Anything else extra is gravy, but not entirely necessary.
No, it shouldn't be something that allows you to walk away for hours or days. Maybe make multitasking easier, like reading, watching videos, or checking the map or galnet, but not REPLACE the player. Furthermore, there should be reasons to not use one, like saving power consumption, mass, and money.
The single biggest balance I could see is that autopilots make the ship susceptible to things like interdictions (or if the interstellar interactivity suggestion I made is implemented, then perhaps it could have a higher chance of failure than a human pilot). Basically, it should be made such that there's always a reason for the player to BE there. If an interdiction happens, for example, then the player can take over and handle it personally. On these long flights, then the pilot should at least have the option of being there more in a monitoring capacity, rather than participating in unending repetitive menial tasks.
Look, how would you feel about yourself if you tried to leave your game running for 8 hours while you went to work, on autopilot, and then came home to a ship that was destroyed because some pirate managed to catch you.
... You'd probably see that, no idiot, the ship still needs a pilot, and you should still be at least present. Otherwise, you lose your ship, and you fail your mission. It's not an "I win" button, lesson learned.