I think trans' make you invincible in 1.3, but only for the first time you trans so you can show off but not whore it, after that you're vunerable. If you're going to be invicible then nobodies going to attack you so you could put lots more flair like lightning and explosions and shockwaves etc.
I just thought of one for Tien's multi-arm form. He gets a huge purple aura, which applies a colour filter to the tien model to make him purple, then the 2 new arms slowly fade in, shoulder, then bicep, then forearm, then finally hands, then the aura changes back to normal and then dissapears.