Wow, elbert, guess I'm more conservative than are you. My recommendation would be for more than one day of local dives before going on the Blue Hole day trip, especially at least one dive to deeper than 80'.
Now having said that, I'll give an exception. Recently met a dive instructor from Argentina. He was travelling all over Central America, various Caribbean islands, etc. and his next stop was Belize. In that he'd been diving at most every location, don't think he'd have a problem with Blue Hole day as his first dives in Belize.
Other than that, I'll hold my position.