The thing is, the exporter/importer descripted in the attached file already exist, i want to expand on it.
What i mean by grouping is, you know, when your in studio max, you can group stuffs(meshs) together in a scene, and then group two or mores other groups together ect, like directory and file in windows explorer for example.
I know the file format seem a bit weird but, it's not that bad actually. im basically exporting mesh data in 3 groups, indexed data for curved stuffs, non-indexed data for blocky stuff (ie cubes), and studio max data required for the importer only. Having both indexed and non indexed vertices might seem like a weird choice at first, but it has it's use. I can choose which mode to use when loading them in my engine. I just made a compromise to use them both instead of only one in the file format, so i can use one code path when importing later, i kinda choosed more flexibility at the little cost of a bigger file size if you want. also, since the file format support compression internally, this is not a big problem.
The thing with cubes is, if your vertices are indexed, you can't use per face lighting, which look wierd, and you can't texture each face independently either, but a sphere for example don't usually require per-face lighthing and using the same texture uv on a sphere work usually well, but not a cube, that's why i export both way.
But, all this dosen't really matter for the question im asking, it's just to clarify the format i used.