Based on the recurrence of that prepared "suite" comment it would seem they have their magic system more or less in mind. Personally, I'm OK with skipping on the Vancian system, but I feel most people's complaints are... uhh misguided, I guess would be the word?
"You don't know what to expect, and thus you may pre-select bad spells" -- that's the whole point of adventuring right? The goal of a wizard (in contrast to a sorcerer) is that they have the versatility to be prepared for anything via a larger spell selection, and as such they shouldn't be wading into a dungeon with all of their 3rd level slots full of fireball. They should include utility spells and multiple energy type attack spells, as well ass support and crowd control spells. The whole point is to be prepared for a multitude of situations.
"I just rest after every battle" -- if you want the game system to stop you from using munchkin tactics, then ok -- just institute a very basic timer that doesn't allow you to rest immediately after resting. Divine Divinity did it, and it worked pretty well. There could be an in-game counter that doesn't let your characters rest unless they either take a heinous amount of damage and/or a certain amount of in-game hours have passed (I am assuming the game will have night/day cycles and so a timer will already be in place). Make resting in dungeons a no-go, it seems suicidal to go into a were-badger Warren and just think "whelp, we don't know what's past that corner to let's set up camp here for 8 hours". The IE style of "you have been beset by monsters" works fine too so long as there's a VERY HIGH RATE of that happening, but I'd also encourage things like the monsters not waking you up until its too late and you're already dead (coup de grace).
"Mana has more versatility" -- mana systems traditionally have far fewer spells because of the potential abuse they can give, especially if it turns into a potion-chugging fest. Can you imagine having every D&D spell and being able to cast any of them and slamming mana potions? Chain-binding meteor storm, abi-dalzim's, and friggin summon spells... blah. Now, if potions and other mana restoration is handled in a way that limits how FAST you can regenerate mana then ok. Something perhaps like the Witcher where mana potions just increased the regeneration rate and couldn't be stacked, so either you had to have the character build to speed it up even more or just wait it out for mana regen. I'd even be ok with something like Kult's HP system where quickly restoring HP led to a lower max hp (temporarily, until you rested) than waiting for it to go very low -- thus risking dying before you can heal.
...err I guess I should post this over there?