Entity model texturing doesn't quite match Vanilla

[stackotter]

Currently some of the entity models (taken from an Optifine JSON Entity Models pack template) have differences when viewed in Delta Client vs in Vanilla. To double check that it wasn't a Delta Client rendering issue I viewed the entity models in Blockbench and found that they looked exactly as they do in Delta Client. As an example, look at the texture on the top of a Blaze's head, the texture is 180 degrees off (or flipped, can't remember) from where it is in Vanilla.

There are a few solutions;

a) fork the entity models and tweak them manually ourselves to fix any issues that we find
b) find another source of entity models (and preferably one in a nicer format, the Optifine JSON Entity Model format is terrible, and has incorrect/incomplete documentation)
c) sort of a combination of both approaches; make our own entity format, export the Optifine JSON Entity Models to the custom format, and then fix the models in our own format

Imo c would be the nicest long term solution, but both a and b would be valid steps towards c while also fixing this issue, so they're perfectly acceptable too.

I'm open to other ideas for solutions too so if you have your own solution feel free to discuss below.