So I've done some digging and some thinking. First, the loaders are already an option. But the problem is that NO loaders connect to buildings that aren't your force, so that isn't really a solution.
So my factories will have to switch forces depending on whose loaders are near or something. But that is no solution because some people don't use loaders. So maybe I'll have to switch when you open the dialog to set the recipe. But I don't know if that'll work right to try to open up the dialog on the machine when it is someone else's force.
I haven't really been actively developing this mod for over a year now, so I'm pretty rusty in both factorio language and the details of my own mod.