I was thinking there could be a new forme for Heatran since it has not been featured yet, and will be in the 12th movie. Now this forme can be kind of unique, what I mean by that is, it will be a temperary forme, exactly like all of CASTFORM's formes. Heatran should only be able to change formes during battle, just like castform. To activate this forme, a new attack, or an ability, such as when Heatran's HP is low, it will change forme, not get stronger, but it will change forme to even out the stats, which is pretty smart idea because you wouldn't want a slow speed when you're about to faint. So the stats will be equalled, I would say that almost every stat would be around 100, higher, or lower.
The appearance of this forme can overtake a dragon, because Heatran's name is a possible combination of Heat and Dragon [From Dran in heatDRAN; as stated from bulbapedia]. Currently Heatran is based on a mythical salamander [stated in bulbapedia], so it would be a good transformation from salamander to dragon! Now during the movie, the way it will transform is different then Giratina's Altered forme to origin forme, and vice versa. It won't LIGHT UP and be all enchanting and whatever, but instead, if you have read Heatran's pokedex entry or the bulbapedia entry on Heatran, you will see that it says:
Heatran's body is so hot that the metal on its body melts and that is why it is somewhat "disfigured."
Well, when Heatran transformes, its body will become very hot, and it will glow red and black, just like molten lava, and it will become DRAGON FORME! The neck could be longer, slimmer body, more reptile-like appearance, bigger, could have wings, maybe, but not nessacary at all.
Now this of course is not possible to happen in Pokemon Platinum because it has not been programmed into the game, and was never planned initially for it, but could be planned for the upcoming remakes of Heartgold and soulsilver! Just suggest some ideas on this please, thanks.
I have made 2 earlier posts on page 27 and page 35, please go read them! they are quite interesting, thanks.