It's interesting you implemented this in Mysql and even wrote a zimlet to manage it. All of the amavis attributes are supported on a per account limit (ZCS 5/6) and domain (ZCS 6) levels.
ZCS 6.0 added webclient preferences to manage the per user white/black lists directly but the admins can modify any of the attributes.
krag_maga: you can set kill/tag levels per user via zmprov
zmprov ma email@example.com amavisSpamKillLevel 3.5
or to bypass completely
zmprov ma firstname.lastname@example.org amavisBypassSpamChecks TRUE