the a7 engine doesn't provide full access to stuff like the assigned textures or bones or animations for a mesh so if you wanted to do a custom mesh loader you would have to write a full .mdl file into a memory buffer and load it with ent_create().

directly using the .blend format would be an extreme amount of work. it wouldn't be worth it. it makes much more sense to use blender's python api to write an exporter.

it would be possible to do it like unity though. start a headless blender from the command line in the background which loads the .blend file, executes the exporter script and then load the generated .mdl. this would already work with the current exporter with some small changes.