You are welcome to do it
So, if I do a local backup, what's the best way to seed a backup copy to another remote repository?
There is no way to map the locally created backup due the metadata difference (if we are talking about backups created on internal storage or shared folders). Backups stored on VBR repository can be moved between repositories and VEB job will recognize that after job reconfiguration. Just make sure that you copied all the backup files with the original folder (or name a new folder with the same name).
Is it similar to standard copy seeding? Would it be easiest to copy it to another local repository, then move the files to the remote repository & just re-map the job?
Sounds good - you should be able to do it.