Ela, I think you system does approximately the same as the SWB version: one locked servo gives half the travel.

I saw your sketch in the last issue of FMT magazine (german). They also explained it works even with one stalled/burnt servo. Burnt servo poses no load on the working servo. You have half of the travel left if it is stalled in the center position.

If otoh a servo breaks at full deflection, you need full deflection from the remaining servo to get back to neutral. Though it is better than no control at all, i doubt that will save your plane if a servo breaks at full down on an elevator...

I like the system though if you have two servos on one control surface. (eg elevator half)