Sure, you can install machinery to do weird fire and gun things. Having your *body* do that is another story: shocker zeds throw lighining with faulty bionics.
Firebreathing is a bit too fantasy.
If bat wings are to be ever useful, you could make them give flight to the player. This would make them useful by letting you avoid mines and pits and later could be easily changed to let you fly up/down z-levels.
This has been considered, one of many mutations that I've not had time to transfer from concept to code. Hummingbird Wings would be the way to go for SMB2 Princess Toadstool* "flight", at significant expense. Larger Bat/Dragon/Wev wings would be along the lines of a glider and would seriously benefit from z-levels.
(Basically, even if you run the wings off the humanoid arms, in similar fashion to birds, you can't get enough lift for a human without a wingspan of around 3x the human's height. Shoulder-mount wings are similarly Large, plus the infrastructure to flap them isn't trivial. So winged humanoids have no chance on Earth of flying...the Nether might have places with denser atmosphere but similar or lesser gravity, though...)
*KA101 pulls up some tall grass, revealing a turnip as large as xyr upper body. Xe deadlifts it overhead and levitates off the ground.
And anyone starting that "Princess Peach" crap, well, I'mma make you eat your vegetables. >;-D