In theory, if you iterate over all roboports and handle those that are mobile, rather than players, this will catch any roboports in cars, tanks, or anything else that has an equipment grid that will accept roboports.

Haven't played with any such mods. You mean https://mods.factorio.com/mod/VehicleGrid?

I already have plans to disconnect the player logic from the grid/entity functions to facilitate automated testing, so while I'm still focusing on optimizing the experience for only players, I'll keep it in mind as a potential future option.