Your analogy is not exactly correct. The bird cage is empty. The plasma is all contained in the wires making up the birdcage. Or otherwise stated, the wires are the plasma. The birdcage is rotating rapidly and shrinks. Also more of a doughnut than a birdcage, as you correctly stated. The plasma strands are continuous through the doughnut hole.
Mr Lerner do the the strands (or filaments) themselves continue to shrink in diameter too?
I think they do. Crushing the mixture causing fusion.
I like your analogy to the 4 stroke engine. It is one of the most successful inventions of all time and is not at all a steady state device.
I’m not sure I would characterize them as old fashioned though. They continue to provide the vast majority of our mobile power needs. Mixed blessing, I know. They also account for the vast majority of our petroleum dependence.