So I've run into some issues with Github.
If you have any required builds which aren't triggered by the staging branch, Github will disallow the merge. This can be worked around but it can be annoying.
More concernedly, if you have any required reviewers, Github will block the merge. You can use the Bors toml file to require reviewers but Bors doesn't support the CODEOWNERS file. This means that you can't require reviews from certain people or teams.
One possible work around, is to have bors squash the PR in-place. I'm not really a fan of it because I don't think Bors should be modifying a user's branch. The other alternative is to implement CODEOWNERS support in Bors.