The reason that I favor a moment connection at the deck (as described above) for a deck stepped mast is the mast will behave like a keel stepped mast in structural terms of being a fixed end condition and so the stump length, or the ability to keep the mast up if a shroud parts, in theory would be the same as a keel stepped mast. But with a moment connected, deck stepped mast, offshore if the upper portion of the broken mast were beating the boat to death it can be unbolted and jettisoned.
I think I see where you're going- you're advocating a rigid attachment at the tabernacle? The only issue I see there is that the full leverage of the stick will be applied to a comparatively small base plate which would probably involve a tear out of the tabernacle if a shroud should fail. I imagine it could be engineered to take such a transient transverse load, it'd just have to be larger than the load to failure of the (unsupported) stick.
With modern extrusions, the wall thickness is small enough that the stick usually
tears through under failure, but in the event that it doesn't, I agree that it'd be nice to be able to throw it all away without having to saw through the extrusion. Usually if the failure is mid column without a break, like your scenario, it's best to draw the failed portion toward the boat (halyard to a sheet winch for example) and secure it until the sea state allows for cutting it away.