This is probably just going to be overlooked but I remember that one of the reasons's Rumble doesn't get a lot of skins is because of how his rig works, I believe I remember it being said that one Rioter outright hated looking at his rig. So what's so bad about Rumble's rig that makes it so difficult to work with?
I think that its because his rig only works with the shape that Tristy has, if you change Tristy with a different mech, then the animations of the new mech will look... weird. That is why a lot of people say that the new skin looks "weird" due the animations of the original Rumble.
But that is just a theory.
Rumble's model is so full of constantly moving and jiggling parts. The mech is covered in bits that are bouncing around or nearly falling off all the time.
And you have to reskin/replace those for every skin.
That's my guess, at least.
