How many Acid Damage Type weapons you plan add to the mod? If it's just the plague marine bolter then it's not worth it. If you want to make more Nurgle weapons or early game cultits weapons (maybe tyranids in future?) and make acid resistance armor then it's a good choice. I mean new damage weapon type worth it on;y if you plan make some armor weaks to it and some strong.
Main feature of Nurgle(acid?) weapons can be damage to health/morale/stun before calculating armor resistance (I guess that how Wille Pete grenade from xPiratez works?). It makes this weapon effective against any sort of armor, but not leathal. Also it will require some thing to restore morale of troops, and Battle Standart can fill that role. Also acid ammo for loyalist bolters, to make bolter even better then they are now.
Nurgle units - Plague Marine (Nurgle bolter and a lot of blight grenades), Plague marine Havoc (special weapons like plasmagun, melta gun, etc. or Nurgle Special Weapons - blight greande launcher, plague spewer(rapid fire acid shotgun or flame thrower)), Plague Marine Champion(with melee options), Chosen of Nurgle (2 stage unit - first shooty, second melee, works like xPirates ZombieTrooper). Nurgle deamons. Nurgle tank with direct fire plague spewer and indirect fire mortar.
