I'm still hoping that the devs will make Essence important again by making it the per-turn mana spending cap for a given caster on the main map and per-battle cap in tactical mode.
That's an interesting idea - so spending your essence to create new casters, the main effect being that you can cast more spells per combat with those extra casters, is balanced by being able to cast more spells with a single caster (the Sovereign) if you keep that essence instead. It'd make nearly no difference then, entirely up to the player whether you prefer one caster that can cast 3 spells or 3 that can cast 1 each - which is, I think, a good thing, there are plenty of other places to create tough decisions, I'd personally like it if the choice to imbue a champion was purely preference and not determined by game balance. It's certainly better than an artificial limit that's difficult to balance properly, such as a mana maintenance penalty per caster.
Without something along those lines, I don't really see a path to making the magic-focused 'tank' sovereigns that were part of the original plan. It looks like stuff is going to boil down to maxing arcane research and mana production, which for me makes magic feel an awful lot like, oh, the petrochemical industry. Interesting on some levels, definitely useful, but not something given to setting scenes like Sauron losing his Ring.
Of course creating a Sovereign like Sauron is another issue entirely, we need more spells that contribute to that kind of hybridization (i.e. research magic and get ways to become better as a melee, rather than simply becoming a pure caster that relies on damage spells and summons). Not to mention a rebalance of sovereigns/champions vs. units to make wading into melee with one nonsuicidal (i.e. no single unlucky defense rolls getting you killed), which basically means an entire revamp of the combat system.. well much of this is changing in 1.1 anyway, and in the next expansion if not then.