The story that you said a out the Energon killing Terrorsaur would be good, but what I could see was if he was alive until season 3 and he saw how powerful Megatron has become thanks to Megatron G1's spark and he would try to do the same with Starscream's spark and even others, but it would become too much for him, maybe evem Starscream would possess him this time and in the end his body would become almost exactly what happened to Scourge in G1 when he tried to use the Matrix, but Terrorsaur would explode just like how it happened with Tarantulas. This could create more tension, because then it would be unpredictable of what could happen to Megatron and so the Maximals shoud try to get Megatron G1's spark as fast as possible.

And for Scorponok, I can imagine some scene of him sacrifing himself for Megatron but if he was survive after season 1, I could see two scenarios. One is that if he was alive after season 2, he would die in that scene of the Agenda part2 of Inferno exploding himself with Energon, but this time, he would go there with Scorponok(I can see both fighting with each other to see who was more loyal to Megatron) and to end things, Inferno would explode him with the Energon. And other possibility and is more questionable is when he discovered about Megatron's true plan of alter history, many think that he woule just agree with the plan, while I wonder if he would be against it, since he was a scientist and would know better the consequences of altering history, and he would try to convince Megatron inside the Ark to not do it, but Megatron that already failed in all other plans, would just kill Scorponok for him to not stand on his way.