A bit kibbly, but I like it. A bit of a wacky concept, but I'd honestly like to see if somebody could print this up on shapeways, just to see how it may look in person. As far as marketing goes, I'd say Rainbow Dash is MLP's Bumblebee. She seems to be the most popular and most easily recognized. I can't speak for how much Hasbro overstocks her in a case since I don't collect MLP, but like I said, as far as popularity goes people seem to recognize her first.
She's got the most easily identifiable color scheme? She's the only pony capable of Transformer-level destruction without resorting to magic? She once ate Starscream?
Despite liking both Transformers and Ponies... *facepalm.gif* This is a bad idea. The model itself is good, but the concept behind it? @_@
The model looks pretty cool, I'd like to see how it transforms. She tends to be the most popular. She's been one of my favorites since I started watching the show.