Using itemstates with nerdys Gekkio lib animated item or change model/texture in game

I am making a gun mod (pretty usual topic) where you can put silencers and grips on guns and I want it to show the silencer. The guns are animated using gecko lib. Anyone know how to change the texture or model. (preferably with procedures but custom code or plugins is fine) BTW i can't just change the item to a Similar looking one because the guns hold a lot of special NBT data.