I agree that Milton to the PS is a big risk and that Zappe is a small risk. However, without Zappe (or some other vet they acquire) on the 53-man roster, you either send out Maye or Milton if Brissette goes down. If the OL still sucks, that's a terrible position to be in, and completely unacceptable in a rebuild. I just don't see the point in risking the health or development of either of our rookie QBs. Whether it's Zappe or someone else, a cannon fodder backup needs to be on the 53-man roster.
Some folks here are talking about how every position is precious this year, as if this team is making a championship run and we can't possibly carry 4 QBs. To me, that's absurd: we are rebuilding. Without proven OL performance (which they won't have a handle on until at least several games into the season), risking Maye or Milton just can't happen, and if they do it, the Pats are foolish. A serious (or even moderate) injury to Maye will have everyone here talking about how dumb it was to go into the season with the QB depth chart as Brissette, Maye and Milton, given the OL line.