I modified the engine's 1st person weapon code to correctly use random animation permutations (you can all thank Choking Victim for the inspiration and testing to make sure I didn't bork things up). The implementation doesn't require you to change anything, and you just specify the permutation modifier (%) in your animation name like you would for other animations (units, scenery, etc) that support permutations.

I'm trying to figure out where the code is that starts a device's animations so they too can have random permutations. However, they don't seem to be using the same functions as units\weapons\scenery. Gee, my work would be so much easier if I had access to the game's source

I wonder if I sold my soul to Gearbox (ie, landed a job there), if they would let me work on Custom Edition in my free time? Probably not.