It's selfish, but I'd like to see the SNAC change reverted. I've flown bombers for most of the latter part of my Discovery career because I didn't really like much else and don't grind enough cash to get capitals. The extremely high risk, high reward flight style that SNAC bombers had was incredibly fun, challenging and provided a counter to SHFs. Whereas, fast forwarded to now, they're literally guns nobody would ever use as every other bomber weapon has better cap-killing potential and self-defence.
I've mostly stopped flying entirely since my only class/flight style that I enjoyed was nerfed to the ground and I couldn't find anything else that fun, in essence.
On a bigger scale, "dungeon" systems. Very dangerous places with randomly spawning loot, RP cargo, NPCs with their own loot. Like Unknown systems, but further away and genuinely worth a visit. Something like Sombra's idea. Since we have a few people who make systems and places without actually asking devs to implement them, it could be on rotation to showcase their work or temporarily bring back closed-off systems from previous versions of the game.
Lastly, and it could go hand-in-hand with dungeon systems, research ships. While this would probably need FLHook magic, it'd be amazing to see and give people another venue of RP/income gain and moneysink/rare loot. I've heard several versions of this, the main one I liked is that there could be specific "scan" weapons only certain researchy-ships could mount (freighters?). These weapons would then be able to damage randomly spawning anomalies/NPCs/wrecks which are immune to everything else in exchange for data, RP cargo, weapons, customisation tokens for trails/engines, ship tokens or movecharcodes, etc.
It could see a lot of expansion, including inventing "treasure trails" on how to actually find anomalies or where they're located, have events that spawn them as an outcome, encourage visiting multiple systems, do puzzles, calculations, research and so on. Especially since we have a lot of science roleplay fans, I feel like this would really drive activity and interaction.