But they're already stronger than Kami-sama
I'm always up for a new animated Dragonball movie but the idea of god in the Dragonball world has already lost its meaning especially in the Japanese version since the nameless Namek was called "god". Then you had big ol' Yemma sitting at his desk to judge whether a deceased soul should move onto heaven or HFIL. Even the almighty Kais, Grand Kai and Supreme Kais are considered tremendously weak compared to the super saiyans during the Cell saga. Or Shin might have just been really weak compared to the other Kais since they could all handle Buu minus his regeneration and absorption abilities.
I just know I'm going to roll my eyes at whatever nonsense the old kai is going to make up on the spot.
Well, it's more of an exploration of the types of gods. For instance, The aptly named Kami and the Kais were "gods" because they were overseers, not necessarily because they were powerful (though the Supreme Kais, and in an anime canon sense, the Grand Kai were meant to be powerful, I still think it applies), same with the Namek. They watch over their specified areas and try to resolve disorder, usually with warriors like the Z fighters.
Yemma isn't really a God, he is simply a judge and only really has power over the dead, as does the Yama of legend and his many variations throughout anime and literature.
This God is the only God that really has immense power, being the God of Destruction most likely inspired by Egyptian (and various other related) Gods and tradition. I don't think any of the Gods, or even the use of the word, is meant to be "almighty" in the sense that the Christian, Islamic, or Jewish Gods are. The gods range in power and purpose and are not solely dependent on having former to fulfill the latter.
I get where you're coming from, but Toriyama isn't the type to pull stuff out of thin air if he doesn't need to. This is an original work made by him, and it isn't forced like the Buu and, to a lesser extent, the Cell sagas were, so I don't really think there's any reason to worry about it being stale or weak in that area.