A Document Signing System will be great for contracts between business, also integrating it with proton RSA Keys.

But for this we should take in count that the RSA Keys will grant enough data to make this kind of signing legally acceptable.

Probably for that an easy way could be a secondary RSA key pair generation specifically for this purpose in order to not affect access to mails or passwords due to RSA keys changing overall in the account.

We could also have an integration to use our phisical identification document rsa keys or even being able to import it to proton pass to make this process easier