In a type-safe environment I think you should just be able to switch your pur sang SQL builder to another dialect. Because of the type-safety you’ll be able to find incompatibilities at compile time which makes the migration easy enough (ignoring data migration). This avoids creating a weird ad hoc SQL dialect trying to fit all the others in a single API.

I work on Mammoth which is a pur sang Postgres query builder, see https://github.com/Ff00ff/mammoth.