G'day Tony,
Using WP:MUSIC as a criterion for speedies would be a disaster. The kind of judgement required by WP:MUSIC and similar guidelines is rather subjective and requires some research to be done--which newpages patrollers are, perhaps understandably, reluctant to do.
Exactly. We need AfD for deciding if a band passes WP:MUSIC --- and, if not, whether we should still keep it.
Getting rid of AfD and replacing it with speedy-if-not-WP:MUSIC would be a Very Bad Idea, for reasons elucidated by Tony and Matt. Getting rid of AfD and *not* allowing the use of WP:MUSIC to consider speedying will just result in the flood of band vanity articles getting stronger.