So I'm guessing that the only way you'd be able to send biometrics to such an airgapped wallet is to collect them from the host system and then pass them through to the guest VM via a virtual serial port.
It's probably possible to allow the vm to port to the biometrics (especially if they're removable or are uninstalled from the host system/deactivated).
If you're wanting to make things a lot more secure and are trying to achieve airgapping on a device you're hoping to use for other things (I'm making assumptions here) you might want to look at having a VM for both.