FWIW, I am building something that fits into the self-custodial bucket as I am defining above.

I will leave the sovereign wallet implementations to the likes of nostr:nprofile1qqs0w2xeumnsfq6cuuynpaw2vjcfwacdnzwvmp59flnp3mdfez3czpspz4mhxue69uhhyetvv9ujuerpd46hxtnfduhspu30gj and nostr:nprofile1qqsw3znfr6vdnxrujezjrhlkqqjlvpcqx79ys7gcph9mkjjsy7zsgygpz4mhxue69uhhyetvv9ujuerpd46hxtnfduhsz8thwden5te0dehhxarj9ekh2arfdeuhwctvd3jhgtnrdakj7qgkwaehxw309ajkgetw9ehx7um5wghxcctwvshspg7dju