WHMCS has a fixed set of DNS record types, which is not supported at all registrars. Currently, our resellers have to modify their clientareadomainsdns.tpl with the supported types, which is not maintenance friendly.
Hereby, I request that you add an additional method callback that returns the supported DNS record types. e.g.:
registrar_getSupportedDnsRecordTypes( $params )
return ['A', 'AAAA', ...];