NFT Game Project

Hey I'm looking for the ability to rank and or de-rank Character NFT(1) stats if you have an Accessory NFT (2) in the wallet of the user. We only need it to change the stats of the NFT and not the image of the character NFT. The Accessory needs to some how be applied to the character NFT and unequip resulting in stat loss or gain and the ability to have the character to be able to apply multiple accessory NFTs to the single Character NFT.
Example: Character NFT has 100 Rank/stat, if the user buys Gun Accessory NFT (separate contact) it will rank and or de-rank by 20+/- so now Character NFT now has 80/120 rank/stat.