Jordan Petridis commented:
Looking at the repository and the requirements I think there might be a reasonable solution that doesn't involve us maintaining a custom executor.
Looks like the way they are testing their setup so far is running podman on host and giving it access to the a big chunk of the system bus so it can talk to systemd. It should be possible to take that as is, stuck it in a VM and setup a VM executor runner (Hmm, looks like only virtualbox is available, meh).