yeah shortly after posting this i spent 2 hours talking with someone who gave me a crash course in understanding what hex is. i was able to get a hex editor and make the edit nfitc1 suggested in the linked post. that eliminated the slash-all addition to the attack slot, but i still need to figure out how to eliminate the all effect on all the other command materia.
master all would grant every spell, while mega-all striped down to only materia functionality would force me to use far more slots. if i want restore, barrier and time for example just for a melee setup thats 4 slots including the mega. master+all does it in 2 and includes every other magic spell in the game. the point is to force me to pick and choose what spells i can fit into the slots, not give me everything i could want and more. the master + all is kinda a last ditch solution if i cant find someone who can point me in the right direction for limiting the mega.