Wouldn't it be better to have the NFC tag sign the event, keeping the key material even out of memory?
Testing an old idea: NFC-based transient accounts: accounts that log off as soon as the app goes to the background, deleting all traces of the account from the phone.
It looks like this in debugging speeds: https://video.nostr.build/ef4274d150303fd28f5e7b6b02a7b0102176263dfb1b491969a0caab6b61e6ad.mp4
If you are an activist and if your phone is confiscated, they will never find anything on the phone. Not even your public key.
Walk around with Amethyst installed and an NFC tag hidden in your clothing. When you need to use Amethyst, tap the tag, insert your password and login. Lock the screen to delete everything.
The NFC has a NIP-49 password-encrypted nsec. If you need, destroy and dispose the NFC tag.
Discussion
The key is deleted from memory. This is not to avoid loading the key, but avoid storing it in the device for other people to find.