Rendering item with conditions [1.15]

I have a simple item texture right now that works perfectly fine. 
I would like to however do an animation behind the current texture but only if certain conditions are met. Meaning this item could either have the current static texture or have an animated one (and you can have both versions in your inventory as well).

I tried looking at ISTER since the shield and trident use it but I assume that is because they have a more complicated 3d model and not just a simple sprite (when in hand). From what I looked at in other mods github repo I need to define multiple layers to my item in the model json but could not find any sort of conditional object.

What I would like (and assumed existed for items) would be some sort of blockstate mechanism, where i could define my cases like variants and have different models for each and then different textures.