You still need a coordinator that has a recent enough view of your utxos in order to construct the tx. So something like BlueWallet. So the only #meshtastic  touchpoint would be after the normal QR-based signing flow with BlueWallet + nostr:nprofile1qy2hwumn8ghj7un9d3shjtnyv9kh2uewd9hj7qguwaehxw309ahx7um5wgknytn6v43x2er9v5hxxmr0w4jz7qgdwaehxw309a38yc3wd9hj7qgcwaehxw309aex2mrp0yhxxatjwfjkuapwveukjtcpzamhxue69uhhyetvv9ujuum5dahx2u3wvdhk6tcqyrevjmyh7eqe55u0sn8nlfewyx2xqhscfqykumj3wrxwtdm8n82qqdfveev : copy the finalized tx from BlueWallet, then relay it over meshtastic to some exit node that can broadcast it for you.