More quests and more inventiveness, more levels, more of everything? That sounds like much work. What about my following idea:

Just go a complete different approach! Make an epic space-shooter with nice planets to land, stations to dock and amazing quests to get. If you can trade, fight and build your own stations then it could be much fun as a MMO. You could meet friends to raid other stations or defend planets, free a colony, whatever.

Something like that would change the MMO landscapes.
But another game with mages, fighters, orcs, thieves and elves - it would only be another competition.

But if you follow this idea then you even do not need this Hero engine, except you want to create detailed landscapes for the planets, but that would be way too much work for an indie studio.