You don't understand Model B, though, if that's all you can say.

In Model B, gravity gets stronger as you get farther away, in at least some cases. (It also might push instead of pull in some cases...hard to tell because you won't specify how anything works.)

You also don't understand Model A, if you think it doesn't fully 100% endorse "collective gravity" with gravity obeying normal rules. Of course it does! It endorses it so much that when the collective gravity isn't strong enough to explain motion, we infer the existence of dark matter to make up the difference.

The biggest problem with your ideas is not understanding physics, but the next biggest problem is not understanding your own model!