Collective gravity is used all the time everywhere and is already accounted for. Do you honestly think that people studying galactic structure don't model the collective force of gravity?! That's literally all there is to do!

Model A is all about collective action, it just is cognizant of how strong the collective action is, and where the actors need to be to exert different kinds of collective effects.

You don't seem to be understanding the structure either of natural phenomena or of your own model. You keep saying "collective action" over and over again, but fail to distinguish between different structures of how actors act.

In hurricanes, there are intense local interactions because molecules smack into each other and affect each other. If a bunch of molecules are going left, and you are a molecule, you can't just ignore them; you're going to be hit and carried leftwards also. Every molecule moves independently, but because they impact each other, you get collective structure. The structure of interaction is local, but the consequences are global.

With gravity, interactions are not only local. Local interactions are strong, distant interactions are weak, but they all count. If a bunch of stars are to the left and close by, but way more stars are on the right yet farther away, you might get pulled right, not left. Every star pulls independently, but because they all pull on each other you get a galaxy: the structure of action is global and the consequences are global.

Model B ignores all this structure, and postulates that despite the relevant force being gravity, the stars don't get to act independently: there immense collusion (but, oddly, only in one tiny little region of space), and the collusion is so effective that the whole is greater than the sum of the parts in perfect cooperation.

But Model B insists on explaining this super-powered magnifying collusion through a force where no collusion has been observed.

And then, presumably because you've been ignoring the structure of everything, you claim that Model B is the simpler hypothesis by Occam's Razor.

But you have to add a new type of collusive collective action, working through a mechanism that has never been show to work anything like that, magnifying its effects where magnification has never been observed, and doing so in a way so as to create an incredibly strong virtual mass which stars can orbit, and to create this virtual mass so precisely--despite radically different physics--that one can use usual gravitational physics to understand the orbits.