Armor: Because FFVII is very modern and such armors don't exist and the game used Bangles as armor, what id do if your wanting to capture that detail is let everyone have a starting "uniform" that they get with their class. Can be whatever they want really within their starting outfit range that you allow. You can go by the alternate pathfinder rules for getting gear and have the outfits gain enhancement bonus' over time of leveling.
http://www.d20pfsrd.com/gamemastering/ot...rogression
Alternatively lets go the bangle route. Instead of straight gear you can give them Bangles. (Leather Bangle/ Plate Bangle etc) Wearing these applying a bonus just the same as their name. such as a plate bangle would act as full plate and such.
Even further, SOLDIER uniforms have pauldrons, so you could have armors come into slots (i think there a rule for that somewhere) so you could wear the uniforms and then pauldrons that give ac but penalties.
Materia and MP: Going with lore, what i would do if i was you is use a mix of the old materia rules. The bigger the weapon the more materia it can hold.
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Light Handed Melee weapons: 1
One handed: 2
Two Handed: 3
Armor: 2
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I don't remember the exact numbers but that's what i would do.
Now MP.
In the game everyone had MP. Here not so much.
Idea 1: Have characters whos classes dont normally gain mp have the Wild talent feat. And gain 2 MP per level after the first. Using this MP to fuel their Materia uses instead of the whole 3 times a day. Additionally for each Materia use have equipped you can attune to all of them, without the need of a UMD check after wards. However for each materia attuned, you gain a bonus mp based on level of materia
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MP Bonus:
Level 0: None
Level 1: +1
Level 2: +3
Level 3: +5
Master: +7
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But they take the level as negatives to damage on melee attacks.
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Melee Damage Negative:
Level 0: None
Level 1:-1
Level 2: -2
Level 3: -3
Master: -4
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Idea 2: As i said above about the materia just without the will talent feat and natural mp gain. But still using MP to fuel the materia. Course, MP cost will be the same for each spell associate with the materia. Such as a Death Materia, even tho its level 3, to cast death would still require 9 MP.
And without the MP bonus, id allow them to use the Materia 3 times a day without the need to spend MP but must pass a UMD check as if their wasnt attuned to it.
Perhaps even allow bangles to add MP for these, idk.
Hope this spit ball helps. If you wanted me to i could try my hand at converting some outfits, but for simplicity id just do whats above.
EDIT: Looking back on it, the negatives would be abit much. So everyone could have multiple materia id say just a negative 1 to damage per materia.
Character with 1 Materia: -1 Melee damage.
With 2: -2 Melee damage
So on.