I think, it would be convenient to have the option to render all tracks into the highest sample rate from all tracks, instead of just giving the info, that an audio montage with different sample rates is not possible (which sure makes some sense, of course).
If, for instance, we have three tracks, one with 44.1 kHz, one with 88.2 kHz and one with 96 kHz, it would be very easy to just put them all into 96 kHz and go on. Without changing the pitch, of course. The same could also be applied to bit-depth, imho.