[1.9.4] Recommended way to render an animated model with a base

I currently have a working turret that rotates, rendered by a TESR that uses bindTexture with a texture map and functions for generating shapes using addVertex. I provide visual cues for state changes by changing the UVs.

First, I've read some mixed information about using bindTexture over some stitched icon functions. So, what is the recommended way to get textures for a model that will change its texture to reflect its state?

Second, should I even be using a TESR to begin with? I just now discovered that ISimpleBlockRenderingHandler is a thing, having not read anything about it since I started working on my mod. And, as my other active support thread indicates, I've also been trying out OBJ model loading to no rendering success (which might be related to my next question).

And, after much investigation, I haven't managed to figure out how blocks like the vanilla enchantment table load their static base while using EnumBlockRenderType.MODEL to render an animated part with a TESR. My turret has a base model specified in its blockstate and another one with its barrel for the inventory variant. The inventory variant works fine, but the base, specified in both the default and normal variant, doesn't render or throw a file not found exception (much like my issue with rendering an OBJ model).

Perhaps I should have split this thread into separate threads, one per topic, but... Eh, ship it. Any suggestions would be appreciated.