I think I have found a way to break the texture size limit (not fully tested).
I tested a few models and they seem to work:
- an opt with 9 texture sizes from 16x16 to 4096x4096
- an opt with 200 256x256 textures
- an opt with 200 512x512 textures
- an opt with 200 1024x1024 textures
- an opt with 50 meshes (to test the mesh count limit)
At offset 19564A replace 81790C000100007717 with 909090909090909090
At offset 1956C2 replace 817A10000100007717 with 909090909090909090
This will disable the texture size check (If the texture size is greater than 256, the game set it to 256).
I've only tested textures with a single mipmap level, so the max mipmap levels count is probably still 6.