Remeber Goris? He had one set of FRMs that he ran around in his robes, when he entered combat the FRMs changed the grey deathclaw model.
If you really wanted to do this I figure that this is how you would do it. Just copy how that did it with goris.
We were looking at doing a similiar thing in Mutants Rising, we were going to use some of the prone and kneeling animations from FOT.
There was going to be a squad of military type people (all highly trained and disiplined), so it wouldnt make sense for them to stand still in combat.
So each of the solider were going to have two sets of FRMs
Goris with robe on = Solider Standing
Goris taking Robe off = Solider lying down
Goris with Robe off = Solider prone
Goris puting Robe on = Solider getting back up
The player would have seen a bunch of soliders and would have been *very* surprised when combat started and the soliders all dropped down for cover. There was two problems with this:
1) It takes time for each critters to 'change robes' I used to get anoyed waiting for Goris to strip every combat round. So I would recomend this fro every fight, as it would just get borring. We were going to use it as a "one off" surprise
2) We never actually tested this theory, but I cant see why it wouldnt work.
Anyway, you could use the same mechnisim for drawing weapons if you want. Just remember that you would need to wait for the player and the NPCs to changes animations one at a time every time you enter combat so it could get annoying (I really hated waiting for goris everytime)