Easy solution: The Seaick Brother Headers were Gosei Green's former Headers, and Megaforce Blue gets them after some revelation over his former partner or something.

Have Green as a temp ranger, and a turtal would be a good zord for a green sea ranger. Also have the turtal turn into a shield for Great, which would look kindof nice in my head.

gosei be 7th ranger

That actually sounds pretty easy, and simple to have gosei green in the show, but I don't think Saban/Toei would want to do any re-shoots of the mecha/zords fight.

In Goseiger, the lack of including Gosei Green was such a huge mistake and merchandising loss. Gosei Green was presumed dead, but he should have been revived as an evil ranger by the villains or maybe just by Brajira as his minion, like the Dragon Ranger, since Goseiger was compared to MMPR so much anyway, or else it should have turned out that Gosei Green, after his defeat and near death, turned his back on the world, decided it couldn't be saved, and actually became the fallen angel that was Brajira showing the two dichotomous routes of Gosei angels. It raises the stakes because it shows that the Gosei angels can be flawed and corrupted.

Anyone ever think Gosei Green will be used to explain why Jake is driving the Gokai Formula?
You know, Jake is made the Megaforce Green to get around that? And he uses the "Voltage of the Eel" to fight evil?
Huh, huh?

That'd make sense.

I've been trying to figure out how they will shove him into a Green Zord Dx.

Though they've recolored zords 20 years ago too so who know.s

saban is not used gosei green footage

i have no doubt that whoever they get the zords from, its a green zord and thas all thats available so its what jake gets.