Using biometrics to generate a unique and invariable key is not a new idea, and it has already been discussed here many times. Such a capability has yet to be implemented.
The same problem occurs here as when using them as a replacement for passwords - anyone with the biometrics, whatever they may be, can impersonate you and do whatever you would normally be able to do with biometrics authentication.
And in the case of cryptocurrency, if these things can be used to generate private keys, then you're pretty much SOL at that point, especially if the biometrics in question is face recognition.