Personally I think they should give you the same number of hearts as the mob you morph into. So being a bat would be super dangerous even with armor. Blazes are too annoying with particles on, and ghasts are way too big for me to ever want to use. Though I like that each morph has a con and isnt just all pros. That's really all the bat is missing.As a reminder, bats were not the only mob that could fly in vanilla; just the only overworld one. Both Blazes and Ghasts can fly, Blazes have the advantage of being immune to fire as well(at the cost of getting hurt from water), ghasts have the same advantage as well, but are massive.