That is a neat build. Seems more of the thing I would run in a pen and paper game than BG3, where I only have control of one character instead of 4. With control over an entire party, I assume that it will be pretty easy to keep my wizard from being attacked, and then all that defensive will go to waste. I just completed a complete a full run of BG1, TotSC, BG2, ToB, and I don't think I had any of my mages cast a single defensive spell once. XD My favorite spell for defensive is to summon monsters between me and the beasties.
Unless you play in story mode, It´s impossible to beat the games you mentioned without some kind of protection against magic spells, true sight, instant death etc and some buffing.
Totally possible. just did it. I'm on Core Rules. I didn't even use any potions that weren't health, removing poison/disease, and occasionally invisibility (like, maybe 2 or 3 in the entire series). As for buffing, I had Jahiera cast Bless occasionally, but I was specifically talking about Wizard protection spells. Never used 'em, never need 'em. My wizards don't often get attacked, and if they do > summon monsters, run away.