!Irish traditional singing is basically unaccompanied, as is its English counterpart; there is no proof that it has ever been otherwise."
oh, you have forgotten Margaret Barry, Pecker Dunne, Luke Kelly,Nic Jones Martin Carthy, Bob Roberts.
MargaretBarry, Pecker Dunne were Irish traditional singers who used accompaniment, Bob Roberts was an English trad singer who used accompaniment, Davy Stewart was a Scots trad singer who used accompaniment.
anyway the argument that you are trying to use "that trad singers were always unaccompanied so it must not change" is a classic example of not allowing a tradition to evolve,
Unless traditions evolve and change and grow they stultify and eventually wither, The nature of a healthy tradition is one that allows evolvement and change.