Apologies, Dave. I could have been a little clearer in my post.
What i was driving at is that by putting a spiral in the gears (as opposed to a simple helix or even no helix) then the the gear contact position can rotate about a point offset from the face gear axis. This means that the bearings can flex a little without causing fatigue hot spots near the tooth edges.
For this application i would imagine that it would work if the spiral centre was in plane with the driving gear axis (at contact centre) and the bearings were allowed to float axially. Any flexure in the casing would be taken up by the driving gear moving about the spiral centre to keep an even pressure.
Gear hobbing of crownwheels is done by a tool rotating at the spiral centre. Since i am not sure how face gear profile changes with radius are generated then i cannot be certain whether what i suggest is practical.