If the choice is between adding a Supercruise autopilot, and an interstellar autopilot, then my choice would be the Supercruise autopilot. Why? Because 95% of it is already in the game. The only thing is lacking is perhaps one minor course correction, and dropping out of Supercruise at the end. It wouldn't be a major change.
An interstellar autopilot would be a major change. Quite frankly, it would automate exploration. Just stick a penny into your keyboard, plot your course, and go to work. When you come home, you've got 300 ADS scans to your name. Easy peasy, lemon squeezy.
Exploration does NOT need to be automated. What it needs is a reason to stick around in a system, as opposed to jumping out. A reason to put down on the surface of a world, or at the very least, a reason to get close and personal.
Most importantly, that reason for doing so should be accompanied by a skill you need to develop. One that requires more attention and input from the player than just honking or pointing at a target that's barely larger than a dot for five seconds. Personally, the time I felt most like an explorer in this game was just after Horizons hit Beta. I spent hours on the surface of planets in my SRV, simply gathering samples and adding my survey to a group project, trying to fathom the mysteries of material distribution. The wave scanner, as an instrument of exploration, is a thing of beauty IMO. All the information you need is there, you just need to learn how to decipher it.
Of course players complained about having to go down and look for stuff, usually in the most ineffecient way possible, and rather than something fun and reasonable, like landing on a planet and taking a few samples to reveal its material distribution and provide another type of exploration data to turn in, Frontier decided to have the DSS reveal all, without ever having to even get close to a planet.
IMO, the advanced discovery scanner was the worst thing to happen to exploration. There is no strategy to develop, no skill to learn with that thing. There is no seeking out of what's hidden from view, because it is omniscent. No feeling of discovery. No moment of "Aha! Found you!"
I agree with just about everything you just said.
At most, the discovery scanner should show you where planets are, and approximately what mass, leaving the rest to mystery till you get a lot closer. Furthermore, the system map should look a little different, and be a bit more intuitive. it should be a proper 2, or even 3 dimensional map, allowing you view exactly where a planet is in the system currently... That matters. If you can see where planets are currently, or at least how their orbits look, and if you have an estimated habitable zone overlay on top of the map... And you see a rocky world of 1-3 earth masses in an orbit that's inside that zone... That's an indication that you may have found gold. That's when you go out to that planet, and start doing more scientific scans around it.
It's this kind of stuff that gets a player thinking, and more engaged.
At the same time however, in this system, it wouldn't be such a big deal if people used autopilots, as any REAL exploration, profitable exploration, would need to be done manually, based on a player's skill and intuition.
Autopilot really is a conditional thing... Maybe it shouldn't be added currently, but after something more is given to the player to do, other than "turn, honk, jump".