We have Ubuntu Core right now,which is made completely out of snaps. However, would snapping things like APT and GNOME be possible? In fact, could you take Ubuntu Core and build Ubuntu out of it?
If not, what stands in the way of this being possible?
There is technically nothing that would make this impossible (someone would have to create a desktop snap with the right content interfaces etc) … practically it is a huge amount of work that will need a big amount of manpower though …
And no, packaging apt as snap would be pointless on Ubuntu Core by design … Ubuntu Core uses snaps only, you would have to re-package things as snap packages (and most likely bundle them by task or so)
I don’t think it would be viable in the sense that we can only change Ubuntu Linux so much before it stops being Ubuntu Linux. That said, yes, it would be (and is) viable to continue expanding Ubuntu Core until it gets fancier and includes more of the platform. Not as a replacement, but as a complement. For example, I really enjoy the idea of being able to develop my snaps in Ubuntu proper and then having a super lightweight platform in Ubuntu Core to put these snaps live elsewhere.
Note that in Ubuntu Core we have a snap named “classic” which brings on board APT and other things into the environment. It’s a bit the opposite of snapd in a classic distribution: instead of being snaps into the classic world, it brings the classic world into a snap platform.
PS. I’ve changed your post slightly to refer to Ubuntu Core, which is its actual name. Sorry if I got it wrong, and please feel free to tweak it further.
Note that we once started such a thing under the name “Snappy Ubuntu Personal” as you can see in this G+ post from 2015
but this was built around the Unity8 technology which then got dropped … just to prove there is no actual technical limitation here …