I find the lack of food and lack of ammo stories a bit contrived. In the prison story line, the group had both crops and cattle in less space. The group also seems to find weapons with the greatest of ease - everything from rifles to RPGs. You couldn't ask for more access to military grade weapons and caches of ammo considering Virginia is home to countless modern day military bases. If you go back to the first season, how many pieces of equipment did Rick walk and the group walk by on the way to the CDC?
It'd be interesting to see the group destroy Negan's base and Negan then occupies Alexandria under a reign of terror with the group on the outside looking in.