Oh, okay, so, on cohorts and mounts as I've been asked. So obviously you can use a cohort for taking some kind of more special mount you might not otherwise be able to get, and considering that most such options top out at various equivalent levels, you would then indeed add levels to them, they would be gestalt levels, and yes, this is sort of the way around the no LA thing, so to note in the face of that:
1) other people do not play your mount
2) It's a mount. There are only so many places you can take, for instance, a dragonne, when bopping around.
3) to be in tune with the feats per level thing, give them a feat per hit die as far as their base state before levels, not every other (so basically double their base feats if they've been built with feat per every two hit dice and don't have some pile of bonus ones)
4) Don't go super crazy with this. A Pegasus or something? An awakened animal? That's fine. I can even live with something with the "half-whatever" templates, depending on the template and some kind of justification (half fiend is going to be a problem for you walking around openly with the thing unless you disguise it somehow). But like.. some kind of multi limb demonic atrocity with multi limb/multi weapon feat shenanigans that you like, stick a saddle on the back of or have shapeshift into a horse sometimes? The GM and Baby Jesus will both cry.