If it is a proven approach I don't know. But my experience with stress relief it needs to heat the whole thing and hold the temp for a while. So I would say it wouldn't do much good, but I never did it. I like the rest of what you said as far as leaving portions of the cut to allow it to cool. Then I would still use the plasma to cut the tabs after. A chain and jack will let the steel know who is boss.
jm2cw