hot damn, I don't think I can do a Hard more and not being able to use items in battle
You'll have no trouble doing it if you have the right materia/equipment and have every character at level 50. After finishing on Normal, you should be close to hitting 50 anyway.
Make sure you have 2 Elemental level 2 (preferably level 3), 2 barrier level 3, 2 prayer level 3, 1 magnify level 3 materia.
Defeating the chapter 17 VR simulator boss gets you an accessory called Gotterdammerung. It refills your limit break over time during battle. If you can get a hold of it, the main story bosses become a joke, with the exception of the last two bosses. Though they're also doable with some careful management of buffs.
Assign Magnify + Barrier level 3 to your healer, and use it whenever the Manawall buff wears off. The VR simulator boss will never be able to insta-kill you. In your ability grid, make sure to acquire all abilities that increase the duration of buffs.