As a special? Maybe not. Transformers, considering you're using the 2007 models, and their battles can be considered too graphic to merge with FiM. If you were aiming for Transformers:Prime, however, that might be able to cut it. Violence isn't totally uncommon in FiM, but if you want to have Optimus ripping Shockwave's head into two, you may be asking for too much. As a fan based project? This can actually be a pretty good idea, but it feels like you're borrowing too many key moments from the 2007 movie, specifically Twilight shoving the Allspark in Megatron's chest, Shockwave's attack on the Wonderbolt base, etc. Try incorporating your own ideas, what if possibilites, etc. You can also try putting emphasis on Pony-Autobot teamwork that can evolve into "friendship" instead of total bot mayhem throughout the special, and how ponies would react to modern cars and trucks in a pony based world. Hope this helps