Also, aren't instructions earlier in the prompt treated with more weight than those that occur much later? Sure, you could insert the system prompt later to avoid re-caching as much, but then the system prompt (if I am understanding correctly) carries MUCH less weight.

(And also your point about immediately being re-cached a good one)

Yes, exactly. This whole complaint boils down to "I don't want my changes to take effect when I make them because I don't expect that behavior."