I'd love new stuff like new ships, modules and wapon, but resonably speaking probably all Egosoft manpower in that department is focused on Split DLC.
Instead of new stuff, I think that for 3.0 I'd be happy to adress some remaining pain points that hurt since 1.0:
1- can we finally have some working mass crew transfer/management/training system - current system would be Ok if not the nighmare of having to go like 7 levels deep into "ship details>crew>crew type> crew list>right click on name > action > repeat" x100
2- I know I said no new ships, but with simple transport/freighter retexture we could add back the TP class to buy/ferry workforce for stations - currently I have megacomplex that need 50'000 workforce, yet after dozen of hours it's barrely at 3'000 workforce. If TP class is too much then at least allow us to shift fund to station manager to boost workforce recruitment.
3- can we update the turret logic to that point that turrets engage incoming missiles if no other target? Currently other than manually set turrets on player ships I don't see NPC factions using anti-missile turret commands.
4- can we adress indestructible stations (mainly Xenon, but probably other factions too) that are under construction?
5- while 2.0 gave L-size turrets proper boost, the M-turrets still seem very weak.
6- Xenon K and Xenon I need several more turrets at back-top section - they have HUUUUUUGEEEEEEE coverage gap that feel like straight cheat to exploit. Xenon I could also benefit to get back missile turrets which it had in X-Rebirth.
7- it might be good to assign some fighter cover to Xenon K and Xenon I to make them less vulnerable. Other factions could at least use drones, but Xenon Capships don't have them.
8- Could we make that defense station and lasertowers actually defend the area by firing on hostile targets instead of doing nothing unless fired upon?
9 - Could we gave some boost to Pirates? Except some random SCA destroyer the lone pirate fighters are no thread to even M-size freighter and I'm yet to lose any freighter to a pirate attack.
10 - also it would be nice if pirates would spawn at pirate stations/free ports and not out of thin air at the gates. I know it might be hard to give them an actual loot based pirate economy, but at least try to pretend there is some semblance

I think 10 is a good round number for 3.0 so I stop here.