Hello again. I fell a little embarassed asking for this. Some months ago I wasn't having this kind of problems and I don't know what the heck happened. But well, let's get to the point
1- I take a race model from 3.3.5 and converted from m2 to m2i with its .anim files using
this M2mod
2- I made minor changes, select all the meshes and bones and exported to M2i again.
3- I used the M2Mod to turn it back to M2 and the modified file had about 1,8MB, while the original one was 2.0MB.
4- Made an MPQ, opened WoW and instead of the model, I have a big pile of nothing. I don't talk about no changes, but no model at all.
5- I repeat the same without the minor changes, just import to blender, export again and turn the file to a M2i file again. Same issue.
PS: I didn't forget the bones in Blender, I didn't forget to move the .anim files when the m2mod creates new ones and I didn't have any problem or error with the m2Mod.