Pubsub with different identities

I noticed you can publish to IPNS with keys generated by ipfs key gen $KEY with ipfs name publish --key $KEY $HASH, but pubsub assumes your self peer identity. I understand the reason for wanting to publish multiple values under different keys, but I’d think having multiple pubsub identities could also be useful in some cases, e.g. ipfs pubsub pub --key $KEY .... Is there some deep reason it couldn’t work like this?