Quote Originally Posted by Revan Ordo View Post
Although my player has mentioned being willing to part with the trap sense ability if that would make this more balanced. Thoughts anyone?
Trap sense is a mechanically useless ability which actually fits flavorwise with your unarmored variant. Your player sounds like a bit of a powergamer. I don't think that you should factor trap sense into any balance calculations.

I also think that losing the natural armor bonus to AC while wearing armor stretches plausibility a bit much. His skin suddenly softens when he puts armor on? Not much you can do about this other than allowing the barbarian to wear armor normally if he takes a feat, or change the type of AC bonus.

About the balance of your original ability, I think it's pretty fair. Your AC will likely be lower in the beginning, and you won't be able to get special abilities later on, but your rage provides a scaling bonus to AC now. Adding extra fast movement into the deal kind of complicates it so you should probably just leave it as-is.