It would be good if LXD (the snap, ideally) were automatically installed and set up for use when using cleanbuild or the persistent container feature. I’m a bit of a noob and I didn’t have LXD installed, it would be really easy for me if snapcraft automated that process so I could just get on with snapping. This is, of course, just a feature request and developers may not have the time (which is fair enough). Might be impossible because you have to install LXD, then init, then add a user to a group etc…
If snapcraft automatically installed and setup LXD you would have a harder time tweaking it to your liking. Once images and containers exist it’s difficult to modify eg. the storage backend.
Although maybe a compromise, like automatically installing LXD involving a UX prompt? This would need some design, though.