It is easier/more maintainable to text 75 people for their addresses every single year than keep an up-to-date address book

Really? You still need to keep it up to date in the year, no?

I suppose the fundamental assumption here is only needing these addresses once a year for a holiday card. That said, what I really want is some sort of iMessage app that pings a list and asks for their address or updated contact card.

Oh then that’s a TON of work to just send holiday cards. Perhaps why I threw in that particular towel. But maybe what you want is the Farcaster Name Registry, extended to names outside FC. ;)