[dredmorbius]

The challenge here is that you've then got to get other people to use the appropriate PGP key(s).

If a key has multiple subkeys, are they all used in encrypting a given message?

That's an aspect of PGP/GPG use I'm not clear on despite >15 years use of it.

[mike-cardwell]

Depends on the implementation. GnuPG picks the most recently created encryption subkey and uses that one. It doesn't use both. Not by default anyway.