I'm not quite as hyped for a trading system as others are, but it would be nice. Personally, I would like to see:
1. Stat system fixed. So many builds have been broken by the cap update. It could be fixed by finishing the stat changes that were proposed, but we've had no update on it for a long time. Basically all non-pure builds are at best, in a weaker position than they were before, and at worst, totally unplayable thanks to DEX still being a requirement.
2. Paxia class and update. I know Ultrapowerpie is working on writing some new content for Paxia, but it would be really nice to see some way for the different clans to actually have relevant, updated gear and gameplay bonuses. A class/new subrace armor would be awesome! Clan competitions wouldn't really be necessary, but there's so much that could be done with the clan bases. Fight battle buttons, clan-themed estates, quests to rank up in your clan like you do the subraces, etc.
3. Some sort of change to the policy of "we never touch a departed staff member's ideas ever again." Yes, this has to do with Archmage, but also with how so many ideas over the years have been abandoned because their original creator left the company. The most recent example of this would probably be the rushed, anti-climactic ending of the Truphma saga. It was clearly something that was just thrown out there because something needed to be done, but no one had the motivation (or permission?) to actually tie up the various plot threads present in that saga. So instead we got a deus ex machina hand-wave of "Poof! Now the truphma and Eukara are gone, the end," with a little tease of more Drakel-Cube releases that never materialized.
4. Class updates. Seriously, this is something I would like to see more than just about any other type of content. They did amazing work with the Werewolf/Vampire/Neko updates, so why not apply those same skills to the other old classes? Having viable, end-game class armors would, imo, add so much more to the game in terms of fun and variety than just constant new GGB armors. Not that I have a problem with those at all, it would just be nice to be able to actually play as a pirate, ninja, martial artist, wizard, beastmaster, etc. in the endgame. And we know that Kalanyr isn't coming back, so for Lorithia's sake just please have the current staff make their own take on Archmage!! It's not like it's somehow disrespectful to have the current staff release their own version of an end-game class for magic users that has been promised for YEARS! I know that vampire and necro will be considered the go-to classes for mages, but it would be nice to have one that wasn't tied to darkness/undead themes.