Once it's delivered the entire runtime / lifecycle / upgrading / bootstrapping is managed by LXD/LXC containers.
It's definitely possible to open up PAKman's support for other build environments. I mean at the end of the day it's just an alpine linux package. As long as you can use alpine's package manager it should work.
https://instellar.app can also serve as a repository for your package. This was an option we considered to enable earlier, but figured people might just want a fully integrated solution.