Nah, maybe some kind of level range requirement, but I prefer the freedom to mix and match. It doesn't actually make sense from an immersion perspective that someone just 'can't' equip something. It's up to you if you're just gonna min-max for optimal armor. I was quite pleased to be able to add a +4 Memory helmet to my mage, or to put the Braccus scale helm on a thief character. If you have the freedom to make any cross-class build you want, it only makes sense you can wear any type of equipment.
