Ok, I have heard enough to convince me that Granada can be safely dropped. However, I am not entirely sure the tag should be used for the Kazaks. I must say that in my games, Russia still does tend to conquer Sibir eventually, so I have few worries about hindering the Bear more, but every reassignment of a tag should be carefully considered.
TRI is a moslem tag, so it should be used for a nation with moslem or exotic type units. The Kazaks are one clear alternative, but there are also some SE Asian states that might be added... So, Kazaks or Siam, Korea or what?
If we combine Catalunya and Aragon, that leaves us with another catholic (or orthodox if it exists from the start) nation. One logical use would be to assign the free tag to New Spain and reinstitute Sardinia again.
After that, all we have left is FPR, which I assume is protestant when it revolts, or converts when possible. It should be used for a nation in Europe; possibly Mecklenburg.
As for the Iriquois, it is true that they are always inactive, but there is not much else that the tag may be used for...