Well the good news is I figured out where I'd messed up - broke my xml syntax. It's easy to make mistakes like that when you're tired. Forgot a beginning <entry> in my store file. Apparently I just need a proofreader.
Now I've got a more... fun question.
I'm messing around with the lasergun arm minigun thing I've seen a few people do. I was thinking I'd move the unlockable one to the SMG slot so they could be dual wielded, and using the unlockable version has the bonus of not accidentally making the murderbots even MORE powerful. I've got everything working for the moment or at least I think I do - last time I launched the game the weapon costume was working fine. Changing the costume entry from the normal unlockable to the murderbot_minigun worked, and the animations are also set by the weapon costume so I've got the DLC minigun using luchador animations while the minigun arm uses the pistol set. Works great. For the moment anyway. Next game launch is going to see how it works when the SMG slot is used.
The thing is, I don't want the DLC version of the laser minigun to end up trying to dual wield, so I'm curious how the flag is going to react with that costume - or better yet, if there's a way to set the dual wield flag through the weapon costume rather than the weapon entry itself. Or really any of the weapon flags.
I guess the only way to know for sure is to try it out with dual wielding on and see what happens.
I'm also considering removing the dual wield flag from the heavy gang SMG and possibly the heavy pistol and then beefing them up slightly to compensate - so many of the gang smg models just don't look like something you should be using one handed ...
Eh. If it tries to dual wield the minigun version I'll just have to ditch the flag and compromise the code until it makes sense with both versions. Or maybe I can move the DLC skin over to a different minigun somehow? I don't know.
Sorry this has gotten really rambling.
EDIT: Solved my 'problem' by moving the Oppressor skin to the GatV Knifethrower. As long as I do the editing in the DLC5_weapon_costumes file it seems to work like a charm.
EDIT2: Dual wielding the newly edited smg/murderbot gun works great. Upgrades work fine, everything works perfectly. Which brings me to phase 2.
I tried removing the dual wieldable flag from the heavy SMG, but it didn't stop the game from dual wielding them. I also tried adding it to the stungun (after moving it to the pistol category as I've seen done in at least one other mod...), but while the stungun moved to the pistol class without issues it refused to dual wield.
Is there some reason the game wouldn't be taking that information from the weapons table, or is this because I set the flag too late in gameplay or something weird like that?