Well if its near on four foot ,then yes you could have a tang ,a juvi majestic angel ,or a couple of dwarf angels.
When you get say a juvi majestic and the book says they grow to 10 inches ,they are unlikely to do that for a very long long time in a smallish tank. Fish that is sposed to reach a foot will most likely get to 8inches from 4 over say five years or so. Exception ime is the Regal tang ,they do grow reeeely quick.
The Majestic or any angel will munch on your corals,less likely than say an emperor,but the possibility is there.
I think and some one will give you a difinitive answer who has had one that the blenny will be fine.
Tangs are safe coral wise ,just consider size. Theres lots to choose from.
Triggers tho they have great temperaments,will eat any snails or crabs rearrange your rockwork and snatch the eggs from your Banghi if you have a pair
Those triggers that are peaceful are a bit big