Yeah, I understand you pain about that. This is the problem with Babylon (and with Three.JS too tbh) models loading follows strict rules. Tbh, I'm not sure how helping you for this specific issue as I'm not a 3D modeler, my best suggestion would be to examine working models (like Duck one) and trying making your or trying to get some help from BabylonJS community.
However, thank you so much for your kind words about the plugin, that's much appreciated!