On-the-fly routing of digital and analog signals using unbuffered analog crosspoint arrays?
Achieving clean passage of an analog signal through an analog multiplexor comes down to this phenomena, which you can model as a voltage divider:

the ratio of signal-source impedance to aggressor-energy impedances

Certainly the signal-source impedance is under your purview.

Crosstalk between the obvious signal paths is also under your purview.

The less obvious aggressors are

1) trash on the analog-mux FET gate

2) trash on the analog-mux FET bulk/tub/well/substrate

Both of 1 and 2 are highly dependent on the quality of RAIL bypassing and dampening.

At high frequencies, the injection of signal-charge thru the signal-gate and the signal-bulk will upset these RAILS, and nothing becomes predictable.

Using minimal-inductance packages and bypass capacitors (and attention to dampening) becomes crucial to analog SNR and to digital DataEyes.