Looking at the UU list, again, I see that there are something like 9 more Knight UUs proposed and 7 more horse archer UUs. This in addition to those already having been created.
This brings to mind another concern of mine regarding using UUs to get rid of horse archer/knights for nonhistorical civs. It means many civs will have UUs arriving at the same times. It sort of belies the purpose of a UU, that being to my mind, giving the civ some sort of strategic advantage for a short period of time. If so many civs have almost identical UUs arrive simultaneously, they become not so much UUs, as flavour units. This can be combated somewhat by imaginative unit creation, but nevertheless, it will create a bit of sameness amongst the civs, and take away a bit from strategy. If you don't want some civs to have horse archers or knights, just make them unbuildable by those civs, at least it many cases. This is my humble opinion.
Nevertheless, I do like the Jinettes for the Spanish and Cataphracts for Byzantium, as well as a some of the others.