Should be easy enough to offer two or three standard settings, selectable by toggling with a button a la Ragnarok. Mode A might be best for classical, jazz fans might prefer Mode B, then there's Baldr's reserve setting at Mode C. And Mode D could be the Frankenstein channel, full user adjustment.
Letting folks roll their own would almost certainly involve either rotary knobs or a screen (which could also display value curves or suchlike.) This might also require a user manual with real lengthy instructions rather than Jason's usual breezy quipfest. Of course, there's endless opportunity for people to get it horribly wrong, but where's the harm if they're playing in their own living rooms? They might even learn something.
Whatever appears should be very cool, not least because it will put the proverbial cat amongst the high-end pigeons. Can't wait.