So it has nothing to do with, say, the order in which I add the attachment slot to ITEMBONES? That should be nice, except for one problem... there isn't an Items subfolder in the Actors directory post-patch! All that's there is the "Monsters" subfolder... unless I botched the unofficial patch+BSM installation??
Regarding my experimenting methodology thusfar: In general my "attachment/gear" tinkering mainly involves the inventory editor and Notepad, but if I need a "live fire" test, I tend to just start up a game and go straight towards the Weird Looking Hooker to take that quest -- since BSM's disabled the vanilla game's starting ambush (I guess because of your lack of starting gear), it's the quickest way I can get a relatively "open air" firefight going.