From what I can see on Process for reviewing classic confinement snaps Mission Center does not appear to fit within one of the supported categories for classic confinement.
Now regarding the ability to manipulate systemd services via a snap - this breaks the snap confinement model and so would likely not be granted (since you could just load and spawn a new systemd service outside of the snap sandbox). So in that case, I don’t think it will be possible to have all the expected functionality of Mission Center functioning as a snap. However, please feel free to open another topic if needed to discuss any additional interface connections etc that may be required as this current thread is starting to get a bit long and convoluted. Thanks.