I think seasons 5 to 7 would be some of the seasons that'd most benefit from Sensei Garmadon being there. Season 11 would benefit from it too. But I think seasons 12 and 13 seem fine as they already are. At least season 12 is fine. I don't think we need Garmadon for that one. I don't even know if Wu had a big role in season 12, so we don't need Garmadon for that one either.
Garmadon being there for Morro's season would be really fun. I still have it headcanoned that Wu never told anyone about Morro, precisely because he was so traumatized by everything. So when Garmadon and Misako learn Morro possessed their child and Wu hid Morro's existence from them...well, it would create some amazing family drama. I also think it'd be nice if we could add something about Master Yang, since that character really needs more lore and stuff.
Also, I think Garmadon being in Skybound would be amazing. Let's say Garmadon went off with the Ninja to confront Clouse, so he manages to get sent to jail with them. He becomes a main character in the story. Wu and Misako are already gone, so Garmadon has to be the team's leader this time around. I'm scared I'm pitching him as a deus ex machina here, but I want to rewrite Skybound so there isn't any time erasal. And if Sensei Garmadon can help me accomplish that goal, then I think we're all in the clear. Also...Garmadon could give us a lore dump about Cliff Gordon being Jay's father. Wu can't, he's gone. But if Garmadon is still available...he could fix things there.
I'm not sure how Garmadon would add anything to season 7, but I imagine he'd just be helpful in terms of giving a new perspective on Krux and Acronix. Wu and Garmadon both fought them, but Wu and Garmadon are very different. They may have unique perspectives on the Time Twins. It'd certainly be interesting to see him eventually interacting with a deaged Sensei Wu. Garmadon can show his paternal side, forced to help care for a really young Wu.
That's why we need Garmadon. He's the secondary old mentor. When Wu is gone, Garmadon can take over. When they're both available, they can complement each other. And besides...garmadon has a different perspective from Wu. His perspective might add something to season 11 or 13. He could talk to Zane during the aftermath of the Ice Emperor arc. He might remember more about Cole's mom. He might have different memories from Wu, memories that could add something extra to the story. I know the writers were probably struggling to differentiate them, but I knew we can do it!
