I've been thinking along these lines also. In this pd-sql rethink, there
are two things that come out for me:

i) We should support the 'query as an argument to the object with
placeholders' syntax, AND the 'query passed to an inlet as a message'
syntax.

ii) We should modularise the functionality of these objects at least
into db.conn and db.query type objects, maybe more. (I know you
suggested this ages ago!)

The design is getting better, the implementation is getting more
tricky ;-)