a massive expansion of the base game......
some examples
1) npcs with skills which you can train on your crew - Elite flavour would be E through to A rating I suppose - trade negotiator, science officer, explorer, medical officer, engineering technician, pilot (we have already), gunner.
then make ships of a certain size need crew to fly - on buying they come with a basic crew to allow you to fly, there is a lot they could do with that.
2) wingmates, some that you can hire to do a mission, alternatively missions to join a wing to do something. sometimes you are wing commander othertimes you do what you are told (complete with basic orders option, cover me, attack my target, go on ahead, stay back etc) like SLF pilot but in a proper ship and able to go into supercruise.
3) more time spent on getting persistant npcs, they dont ALL need to be but some should be, and we get to meet up with them again - sometimes good sometimes bad.
4) another mission overhaul with a bunch of new templates.
the difficulty is charging for this........ a lot of that really needs to be in the base game and i think some would quite fairly expect it to be free which is why i am almost certain 2020 update will either be atmospherics of some description or space legs, then i hope the above 1-4 go in as bonus QOL extras for everyone (but there could be extra crew features IF you have the DLC... perhaps you just get basic crew for free, but if you have DLC you get missions to increase training or to find more expert crew with more than 1 skill etc)