I have 2 Yubikeys which support the OpenPGP card capability. I want to have a robust GnuPG solution which allows me to store one of the keys in a safe place and to carry the other key with me daily on my physical keychain. I want to be able to fairly easily survive having the daily carry Yubikey be stolen, lost, or simply fail, by revoking those keys. I also want to be able to survive having the safely stored key fail by revoking those keys.
My original plan was to create a main key pair and 2 sets of encryption and authentication subkeys (4 total, 2 enc and 2 auth). The main key pair and one set of the encryption and authentication keys would be transferred to each Yubikey, so each Yubikey would share the common main key pair but have a different set of encryption and authentication subkeys. This turns out to be quite difficult to implement in a secure way due to how GnuPG's key-to-card functionality works. GnuPG expects if you transfer a key to a card that you want that key to only live on that card an