Polygon Count is already addressed with creating 3D Items, which Item Forgers do Outside of Toribash. Likewise, creating objects and then importing them into Toribash is already an achievable feat. However the difficulty comes from importing them into the Modmaker, so your availability to modify the Toris themselves stays constant. Else, mods created outside of TB would be limited purely to objects and none else. Unless objects can be directly ported in and out of the Modmaker for consistency's sake, this feature likely won't get implemented. For Toribash at least, I don't think we'll see Feature updates until TB Next, especially not updates for the dated Modmaker.
Nevertheless I agree that this feature would be super useful for mod creation. I would be able to goof around with Blender/3DSMax and create something cool, whereas with the Modmaker I'm limited.