MEMS switches are very sticky (van der Waals forces), I understand they have problems with consistent operation. But yes, it has been tried! Excellent on-off ratio (including at AC, i.e. low capacitance), as you would expect from a mechanical switch.
I wonder how fast they can operate. kHz certainly, but maybe not MHz. Much larger scale size as well, um per transistor rather than 10s nm.
Or speaking of which, can they do nano-MEMS these days? I haven't checked. With everything just completely bathed in proximity forces (and with such small levers compared to the contact areas, even direct chemical bonding will be considerable) I would guess it's not likely any better behaved.
Switches can possibly be controlled in an analog fashion, van der Waals forces and such notwithstanding, as tunneling current appears before direct conduction does.
Tim