grarpamp:
Yes if you intend to patch tor to use a smartcard as a cryptographic coprocessor offloading anything of interest that needs signed / encrypted / decrypted to it. The card will need to remain plugged in for tor to function.
As I said before, only thing that actually needs to be protected here is "main"/"frontend" .onion identity. For that purpose all you need to do is to sign descriptors. And not to lose the key.
grarpamp:
However how is "pin" on swissbit enabled? If it goes from the host (say via ssh or keyboard or some device or app) through usb port through armory to swissbit, that is never secure.
No, I will be secure. An adversary could sniff your PIN and sign whatever they want to, true. But revealing the PIN != revealing the key. In this case your identity key is still safe even if your PIN is "compromised".