That's the hard part of adapting an already existing game xD
I think Edron really is the perfect next addition for the exact same reasons you said! It has a nice progression, nice bosses and quests, and it isn't end game already opening space for other future additions too. I could even add a small hall of fame for people who manage to kill Orshabaal, but that would also require some anti cheating checks to make sure it's a good leaderboard lol