Interesting. Read through the comments and the cache issues and context loss issues were already mentioned and they are all good valid points. I'll go from the positive side.

I think the part that resonates most with me is the deterministic rule based routing. It can even double as a policy that you can audit. Configuring which calls would go external and internal.....this could work well for companies who want to enforce certain privacy policies on what data goes to external frontier models vs internal local models. I think the privacy angle is stronger here over the cost angle.

I believe a config-led setup is the way over a model trained on routing. Opus (I'm most familiar with) and I'm sure other models already have the subagent spawning skills down-pat. I basically do a similar routing by config setup but using Claude with some rules and a framework.

So if any routing is needed it might be at the point you've identified....locally on device config-led. Neat. If I get the chance I will check it out and give it a whirl.