I like the idea of sub-stat materia, but the ideas you've proposed I don't find interesting at all. For elemental material, if I use wind materia against garuda I take what, 2% less damage? The amounts would either be so small that it wouldn't make any difference anyway, so high that they were content breaking, or if it fell between these amounts, the content would have to be adjusted to assume everyone had this buff, which would make it mandatory, everyone would have said buff and then it eliminates the whole point of it anyway, if everyone has the same added shield.

Sorry to be negative, but I don't really like the resistance ones either. Firstly if I get hit by a debuff like stun or something, it's usually cos I've messed up a mechanic. and if I wore a sun resist material I would subconsciously expect it to save me from every stun, I mean if I had a stun resist material and you still get stunned anyway, I'd be annoyed and thinking why do I even bother wearing this materia

I'd rather materia that had very low chances of proccing something. So low that it could never be relied on (and so not be one of those things that everyone simply had to have), but on the very rare occasion that it does, it could be fun. As BLM, maybe a materia that gave me a 1% chance on each fire IV cast that I get a "triple" buff for my next cast and it hits three times, or a 5% chance when using a thunder proc I get internal release buff, something I wouldn't normally have access to. idk just example ideas off my head. There could be lots of different types of materia like this, but by making the proc chances very low, it's hard to say which is strictly better, and so hopefully would be more about people picking whichever ones they found more fun, rather that there being one obvious best materia that everyone would have