>At the moment, the answer is a somewhat unsatisfying "I'm not sure."
>It would be technically possible for any number of his family and
>friends from The Future to attend, since he knows four Time
>Lords and any number of major and minor divinities and infernalities,
>any one of whom could probably arrange it alone with effort or,
>working together, with minimal difficulty.

Yeah, the main universe is one in which gods and beings indistinguishable from them walk among the mortal world. This one feels more like one they've abandoned and the mortals and minor supernaturals are keeping it running as best as they can. Gryphon, despite his supernatural powers and experience, is just a man; he fights and teaches as hard as he can, but his lever to move the world is shorter than people like Utena or Korra or Corwin.

>The problem I face in deciding the matter is rather one of
>tone--would it mess up the feng shui to cross the
>streams that extravagantly?

I feel like it would. The sheer number and magnitude of the visitors for any cross-dimensional wedding ceremony would draw the Neuroi, who would get their shit kicked in thoroughly, and then Utena in divinely created Swordfish II strikers and Kozue with a jetpack would lead the charge that sweeps them off the world entirely. And that'd be unfair to the girls of the 501st who've worked so hard for the victories they've gained.

>After all, part of the charm of the
>OWaW/GG setting is that Gryphon is operating without most of that
>hugely elaborate background network he has in the 25th century.

So of course he makes a new support network, and of course it's largely made up of cute girls. Raise your hand if you're surprised.

The other problem is that, not only is it possible for his family to attend, it's all but impossible for them not to. Tracer here knows that G is getting married, and what she knows in one universe, she knows in them all. We've already established that time flows differently here than in the main universe, so there are no time constraints on who can attend. The dei and machinae involved would require another deus ex machina to keep them out of the equation.

I'm reminded a bit of Transformers: Flesh and Steel, where a Kilrathi war is used to keep the rest of the WDF out of the way so the crews of the Axalon and Darksyde can develop as characters the way they're supposed to.