Most f the things I can think of are elaborations on mechanics that don't exist yet or may never exist.
-Disable and board someone's ship, imprison and sell the people on board as slaves. You or your NPC copilot could fly it back to a station and sell the ship or keep it. Huge boost to piracy profits and incentive.
Two words for this: Self Destruct. I would rather die than give up my ship, and if I can take you with me, so be it.
I would abandon Elite if this were implemented.
Things I would like to see:
Personal storage - A place to store plain old stuff. Why? Because it happens often enough that we need more space than our cargo bays allow for things relevant to missions. Mining missions come to mind - collect 80 Methonol Monohydrate Crystals. Yes, I've the cargo space for 80, but I also need room for Limpets, and the more of those I can carry the more I can mine, so if I can store say, 60 tons of MMC, I can carry more limpets, which means I can mine more MMC, and then when I'm out of Limpets, I can retrieve the ones I've stored.
Personal Base - A place to land without having to ask permission first. Who wouldn't want that? A place to store my extra ships, display accolades, or simply park myself without having to worry about anyone else complaining I'm hogging the landing pad.
More complex and detailed missions - We have a good framework, now just add the meat and potatoes.
SVR Trailers - Things to pull along behind an SRV, preferably things with additional cargo space, because 2 tons is just not enough.
Surface Mining - Not blow up a rock, but actually find meaningful sized deposits of materials.
That would suffice for now.