There isn't a simple way to do this that I know of. Local is treated differently and the literal repo name "local" seems to be tied directly to both the default and handling the repository as local only.
You can remove the local repository with some database shenanigans on the scm table. that will remove the default entry and require you to select the repo to store the content in. If you add a remote repo after that with the name local, that repository will then be the default but because it is the "local" named repo, the platform will not execute commands to sync updates made to that repo to the remote repository. You can ssh into the system and run the push commands yourself but that would be a fairly tedious process.
I think your best option if you really just didnt want the local default would be to remove the local repo and manually select the correct repo every time, but that isn't going to gain you much other than preventing accidental commits to local.
