Eee, Atlas lion mane<3 That's the sort of thing I wish we had, too, because that's supposed to be the type of mane my winged lion has.
While at our current place we can't add this to the game, somebody making an add-on (like an item) would be cool. Although, the problem I foresee with that is that the add-on mane won't bend with the character because it's an item). So, if they sit down, they might just have a mane sticking through their back. ;P
Definitely a nice idea, though.
It would be nice if we could though, it would be something different. I see with what you mean by add on too, just wish things weren't so dain complicated. My fursona Dorian also has a mane that meets half way to his stomach.
