I am considering giving my sister/husband a night at the local Hyatt for Xmas (to be used at their discretion). Anyway, I know that award stays can be transferred, no problem. But the GP T&C state tier benefits are not transferrable? Is this written in stone? I would like them to be upgraded and also receive Diamond benefit (amenity/breakfasr certs - no RC so that's no prob).

Has anyone ever done this? I know that I could go and check in and give them the key, but is there any other way around this?
Thanks!