Yeah, I think this might go along with the inventory system than a character controller. However, I have seen assets that are even more remotely related to UCC or TPC to have mind blowing integrations (such as DSU, Malber's Horse Animset, etc) which opened doors to possible behaviors that would be very difficult to integrate otherwise.
For UMA I was wondering if the item pickup component (or an additional component) could be integrated into UMA's runtime recipe changing method, so that a costume kit could be picked up to replace the current one.
Another idea is to integrate the weapons and shield made for UMA to work with UCC. These are not models or prefabs per se, so cannot be introduced into the UCC's current item building system.
But when I look at it, this does possibly sound like an integrate that may make more sense to be done at UMA side.