Phacility was very much against this kind of things, but I actually favor supporting some packages, at least for Arcanist on the big package-managers - if nothing else, it would allow us to make sure the package with the right name is doing the right thing.
I'm less happy about trying to maintain a Phorge package, because that's much harder to customize to a specific install's likings.
I don't know what it takes to actually maintain a Debian package.
The only trouble with maintaining a separate arcanist package is keeping the version in sync with phorge. Phabricator never followed anything like semantic versioning and there was never really any stable api version to depend on. Perhaps we could think about versioning and release cycles that follow a more predictable major version release cycle with API compatibility guarantees. It is certainly more convenient (for the upstream) to avoid all of that but it offloads quite a bit of burden on anyone trying to use the software.
Maintaining a debian package for arcanist wouldn't be terribly difficult, though debian packaging in general is (in my opinion) annoyingly archaic and cumbersome.