That's a really interesting idea. I can't answer your questions but
intuitively I think you have got a point. Whether it makes any
difference at all in practice, I wouldn't know. The thing to be do, I
suppose, is to try an experiment, fixing as many variables as
Apart from the bubbles issue, it certainly seems to me that having the
entire base of your kettle heated by some external heating method
whether it's an attached electric element, a propane burner or kitchen
hob will mean that a much larger proportion of the wort is in contact
with the heated metal.
Using a heatstick (and I've never tried one) it would seem only a
limited amount of wort is heated and without a fair amount of stirring
you could end up with cooler areas in the kettle.