Here is what i wish for TF 3 :

Unicron and Primus (they had the same size as Optimus, may be a little bigger) were the greatest warrior in Cybertron but Primus had to fight Unicron for his menace in Cybertron. Unicron then burried under a volcano on earth. Megatron knew the location and tried to revive Unicron by taking Starscream's spark (Megatron killed Starscream). Optimus knew the plan and fought Megatron and he won. But too late for stopping Unicron. They fought and Optimus lost (but not dead, only damage very bad). Unicron reconstruted Megatron into Galvatron and looked for Sam for the last fragment of the all spark to stabilize Unicron's power. Optimus was brought to NEST HQ and given a new body, a SUV/MPV car. Unicron and Galvatron came to NEST HQ and got the last fragment. Unicron also revived Optimus damage body into Nemesis Prime. Then, the battle began.....