Build a "proper" kernel package
Debian's kernel package does more things then "make deb-pkg" can provide. See
https://kernel-team.pages.debian.net/kernel-handbook/ch-common-tasks.html#s-common-official
for how this would work. This package could be uploaded to the PureOS repos.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information