I don’t think we’ve tested it, but I believe it should be ok.
Campaigns are indeed not included in the overlay schedule, as it’s not designed with them in mind.
I think what would help you is fully implemented playlists feature, but that will come in 1.9 series - I appreciate that it’s not really helpful right now.
If the overlays scheduled like that look good for you, then that could be a good work-around ish for now.