Maybe it's just me, but something I always found lacking in most TES games is the Mage class. Now, I'm not for one second saying there haven't been viable mage builds, there has been, however, the class in general just feels lacking compared to rogues and warriors. Whether it be the in-combat mechanisims (dire regen etc), high magicka cost or the lack of skill scaling we witnessed in Skyrim, I just feel the class in general isn't given much love by the devs.
Regardless of what you think about the game in general, ESO just does this particular aspect a lot better, the difference is night and day. Playing a magic centric character in ESO is just a lot more fun. It doesn't feel like you've been placed at a disadvange, the mages/sorcerers just feel a lot tighter if that makes sense. You just get the general feeling you've opted for a class that's on par with every other class.
My point being, I think Beth could do worse than implementing some of love mages/sorcerers recieved in ESO.