I've personally not spent too much time fighting any migration tool. Configuring Alembic from scratch, for instance, takes about 5 minutes for separate dev and production databases (MySQL/SQLite). Code-generation comes as a bonus. There's 0 chance I'd trade a day of developer time to build an in-house tool re-creating 90% of what Alembic does, with its large audience use-testing it daily, stability and documentation.