Personally, I think this:
1) It is extremely expensive to get hold of a harpischord.
2)Overlapping notes can easily be resolved in nearly all cases.
3)There is no huge difference between the pianoforte and the harpsichord.
4)The pianoforte is a vastly superior and easier to handle instrument.
5)I have heard much professional Bach on piano.
6)There is no sound quality lost, as a piano can do everything a harpischord can, and more.
7)If the said piece is an ensemble, piano/harpischord will barely be heard most of the time anyways.
There, I've countered all your points and given my own, Sylvia. If you can prove me wrong on more than half my points, I'll gladly agree with you.
By the way, "clavier" simply means "keyboard".