But have you done a remote QR-only cosign where you send and receive animated QRs as videos?

Cosigner doesn't even need any wallet software. Record the psbt's animated QR and securely send it to your cosigner. They scan it, review tx details on their @npub17tyke9lkgxd98ruyeul6wt3pj3s9uxzgp9hxu5tsenjmweue6sqq4y3mgl , sign.

They record the animated QR of their signature and send that video back. You show that QR to your coordinator software and broadcast.