Native PKCS#11 support, by attaching any module/library, without having to use workarounds (alternative gpg-agent etc.)
The problems faced when trying to use any other card than the OpenPGP Card are simply too great and reuire lengthy workarounds. The average user won't be able to do it. There was no reason for creating a separate card standard, since PIV and PKCS#11 already exist. And, truth be told, PKCS#11 has taken over and almost all card manufacturers support it. Supporting PKCS#11 will simply boost GnuPG penetration and lower the barrier for using it with secure elements.