All very interesting thanks! I agree that it's good to maybe bring in more decoration/ornamentation second time through a tune, as well as keeping the rhythm throughout. On the same premise, you might bring n harmony 2nd or 3rd time round, or even do a change of lead instrument for variety.
Ornamentation can be very instrument-specific: what may be an easy "turn" or mordant on a fiddle may not be so easy on an accordion if it involves directional changes on the latter>
And Alistair Anderson does play Northumbrian pipes as well as concertina, with there being quite a lot of ornamentation on pipes.