General-Purpose Hardware Wallet
Use (or modify to use) the Ledger to perform general key generation and signing?


Yes. The things that the Ledger support are not specific to cryptocurrencies. You can write applications for the Ledger that do other things, so long as the firmware supports the cryptographic operations that are necessary.


  : Buy a general-purpose keygen + signing device that supports crypto-currency signature methods?


Yes. The cryptocurrency stuff happens externally to the cryptography. You can write an application that offloads the cryptography to a general purpose keygen and signing device (usually HSMs) and handles the remaining cryptocurrency stuff (transaction construction, node, etc.) on a general purpose computer.



Hardware wallets are really generic HSMs (although the Trezor does not contain a secure element like Ledger Nano S's do) that have had specific cryptocurrency applications built into them. They can be used for general cryptography things too, you just need to write software for that, and possibly modify firmware.