Without going into how this won’t change combat much, I want to go into your material ideas rather than the ideas themselves.
Deathblow- sounds too much like an instant kill. Also, sounds like a Direct Hit/ Crit... I’d be fine with a stat that increases both’s chance to hit at the same time slightly, but I feel like that can already be done to a pretty decent degree without something like this.
Multi-hit - I’m not against something similar to this. This sounds fine. I’d just change the name because FF7’s Materia names were really simple and unappealing.
W - magic - I see a lot of people having issues with this seeing as casters are already some of the highest damage dealers.
W - Item - I’m not sure about this one? I feel like it’s pointless.
Sense - First I’d change the name to Scan since that’s a common spell name in the FF series... but even then, it’s kinda a pointless buff.
HP - Plus - we have this. It’s called Vitality.
MP - Plus - we have this. It’s called Piety. I wouldn’t mind it if Piety affected more than just healers however, personally.
Damage Plus - once again, not opposed but I think having it be a full stat and give it a more appealing name would be better.
Counter - this would make Vengance pointless on Warrior, but if they find a way to rework parry and make it a counter system I wouldn’t be opposed... I’m just not sure everyone else will be okay with it.
Magic Counter - make this one stat with above, call it parry
Haste - Skill Speed and Spell Speed, already exist. Now if they made them better again, sure.
Tenacity - I would actually like this better than Vit mainstat. It does something compared to Vit.
Spirit - you literally just renamed Mind and added a reduced MP cost thing. I’m not sure how that would work, but okay.
Blessing - sure. I guess. I don’t know.
MP/STAM Absorb - no. I feel the systems are fine as is.
Focus - Wait, isn’t this essentially the same as “Deathblow”? Oh wait, it I crases how much they do? Sure? I feel like others won’t like it but fine whatever.
MP Turbo - many MANY people would be against this one I feel. I’m not sure myself.
Your “need ideas” ones sound like they won’t work.
As for your “upgrade system” I feel you’ve played too much FF7 and not enough online games. But that’s just me.
Don’t take this as an insult or attack on the post as a whole, this is me criticizing what I see and how I see people reacting to it.