The rebuild is never complete and no team in the NFL is "deep". The Pats went on a 9 year drought from 2005-2013 because they had holes in their rosters over the years.
This current Pats team has a major weakness along the OL which could absolutely derail their season. Run defense at both edges is the other. Ellis next to Spillane is the last. He will be dependent on Spillane staying healthy. I'd prefer the Pats bring in a veteran for at least early downs.
Talking about fringe practice squad players is the wrong conversation to be having when we should be discussing their actual starters.