First time hearing of subkeys on nostr (njump link below by npub1melv683fw6n2mvhl5h6dhqd8mqfv3wmxnz4qph83ua4dk4006ezsrt5c24)
Nostriches need the ability to change nsec keys and have "their account" carryover in full. If my nsec is compromised, or I think it might be, I'm out of luck. Currently, nsecs are burner phones. You use it until you feel it might be compromised, then trash it and start over.
I've used Hive (formerly Steem) since 2017 as a blog. It's possible to generate new private keys and everything account-wise carries over. Also, there are actually four keys from least to most secure:
Posting - to post stuff
Memo - send dm
Active - move money
Owner - control everything
Users can chhose which dapp gets which permission/key, or not.
Maybe subkeys could be used similarly on nostr, at least to a degree. I'd especially like to see the ability to migrate to a new nsec if needed. Nostr Wishlist