I have some extra bits on stations that would be useful for other stations, but I see no way to make this happen.

What do you mean ?
You cannot auto request materials for construction using P2P (it's just not possible). But you can create a new platform, and make requests from this new platform using P2P.

Oh, I see--turn off any silos on the planet and copy the requests to the general group.

Couldn't you scan the blueprints on the station to manually make a list of required items? Then you could have a toggle "request required items from stations" analogous to the vanilla function...

This is not a feature that is planned for the mod, right now, but it may be possible. I'll keep it in mind for future versions.

Would you be interested in a PR that implemented this? Since your mod is licensed under -ND-, I can't fork it, and I'd definitely not make the effort to implement this if I couldn't share it with others.

I'm in the process of a huge rewrite of the mod that would make it more extensible. I appreciate you respecting the licence :).
Once it's done, I want to plan for a plugin system that would allow modders to add functionnalities, or, open the code if I'm confident enough it's not too dirty.