So, I put way more thought into this than I probably should've. First off, this game (Let's call it Final Fantasy 18) would feature a weapon system where each character only has one weapon, but it can be modified (improving its base stats) and Customized (giving it special features). Modifications are permanent upgrades, but Customizations can be added and removed as much as the player wants, with each Customization deducting a certain number of 'Customization Points' or CP from the total available to the weapon.
And now, the 'characters'!
Machinist: The main character, an inventive young man and aspiring engineer. His "Techs" are all various personal inventions of his, and most of them can only be used a certain number of times per battle. His weapon has the most CP out of any of the characters, at the cost of also having the lowest base stats (Though, with the right Customizations, this isn't that big of a deal), and his "Mix" ability allows him to combine two items to create a new and more potent item, which is immediately used.
Cyborg: A mysterious young woman found in a pod in the ruins of an ancient city, highly advanced civilization by Machinist. Most of her techs actually require HP rather than MP, though her special ability "Recharge" (renamed Chakra) can be used at any time to restore a percentage of her HP. Her weapon has the highest base stats of all the characters, but also the least CP, a mirror image of Machinist.
Red Mage: A handsome, gentlemanly traveler with a bit of a womanizing streak, he joins the party for reasons he keeps to himself, though he seems to have an interest in Cyborg that goes beyond aesthetic appreciation. Like any good Red Mage he combines offensive and supportive magic with physical prowess, and is the first party member to use 'traditional' techs in the manner that they all cost MP. He also possesses the ability Runic, making him ideal when facing spellcasting foes, as he can both protect the entire party and replenish his own MP stores at the same time.
Scholar: The last party member, she is a scholar (hehe) of the same ancient civilization that built the city Cyborg's pod was discovered in. She's a bit odd, having spent more time around books and ancient artifacts than actual people, but tries her best to help despite this. Like Red Mage she uses regular techs, but has a much wider variety available to her, at the cost of lower physical prowess. Her unique ability "Libra" (AKA Peep) allows her to ascertain the strengths and weaknesses of her target, a handy ability when facing powerful foes.