Yes, I see it as the only logical solution really. One of my nearest stations, New Malden recently had the rear entrance gated but they put the barrier in a position such that an entrance which always had people coming from 2 directions can now only be accessed by 1 if you want to use contactless. This means there continues to be many fare dodgers who just don't go through the barrier and are never questioned by both agency staff and poorly handled the occasional time there are agency ticket inspectors which seems like a real waste.
On 701s guards will be able to easily walk through and check tickets and as you said the simple presence of them on every service would deter fare evaders however it then becomes a question of if guards keep their door duties or if that's passed to the driver whilst the guards become OBS instead essentially. It seems like a logical middle ground in my opinion at least however both parties have to learn some communication skills for it to ever come about. I do doubt they haven't come up with this solution already however but it must of been rejected by one of the 2.
