How to support more vectex with mdl7 file?
If any mdl's vectex exceed 65535, the game engine will crash.
My sandbox game merge some entity model to one model.
The 65535 / per model is very restricted.

That's the limit, you cannot use more than 2^16 (limit of unsigned "short") per vertices per model.
You have to create several models instead, i.e. create your environment in chunks.