just just grab the multi-part bundle of line, duck and flip it around the pedestal while the boom goes crashing over in 20+ knots of wind.
Apparently that's the way it is done.
Yup, that's the way it's done. You don't have to grab the entire bundle; you can hold & pull on just half at a time. That brings it in pretty quick, and the line running back through the blocks dampens the snap when you release. It still helps to be quick, though.
On the initial post, using the traveller to absorb some of the energy in an inadvertent jybe may help keep from damaging the rig, but the swinging boom is still dangerous. Rigging a preventer line, as you suggest, is a better idea. I had a friend knocked overboard one night, surprised by a swinging boom. They never found him.