Check out RooCode if you haven’t. There’s an orchestrator mode that can start with a big model to come up with a plan and break down, then spin out small tasks to smaller models for scoped implementation.
If you’re open to a terminal-based approach, this is exactly what my project Plandex[1] focuses on—breaking up and completing large tasks step by step.
1 - https://github.com/plandex-ai/plandex