I've uploaded this to batfactors:
which ought to handle everything but the monster's unique attack damage, which has to be hardcoded in BatBrain. I've added the code and it will be in the next update.
monster 1210 blazing bat 5 none,hot,spooky,stench,sleaze autohit, dodge 1.0
I hadn't checked mafia's data, but Crowther is quite right, the physical resistance and default monster element stuff is taken from mafia's data, and information specified in batfactors simply overrides existing data. The "none" above could be omitted (in which case the 5 should become a 4).
EDIT: And r109 adds the blazing bat's attack and makes the "dodge" keyword work for the weapon attacks listed on the Wiki, not just "attack".
It also adds a patch submitted by someone, somewhere, somewhen (search can't seem to find it) for the short calculator, so that it only works vs. pygmies and delevels the correct amount. You can all un-blacklist your short calculators now.