and if you wanna keep the "using items'" part of it without actually having to constantly refill them the just do what FFX-2 did, "Use spare potion that you tucked away," that just changed it from having to buy items (which would just suck and makes no sense) to making it an ability... TP based healer!!
ALSO you can throw in the "mix" ability which has endless possibilities. OH and they can use the Phoenix Down in battle (with a CD of course)
edit: ANNNDDDDD they use guns of course, BOOM your unexpected new gun-class :P