It's just a suggestion. Can the cache just support some "customized-specification mode".
For example, cache a page with more related posts to a new comer (if he's from a search engine) and cache another normal page for those old friends. And cache a page with even no sidebar for those heavy readers (who only cares your post itself).
Or, cache something for IE, something for FF, something for iPhone user-agent.
This feature would be a little more advanced and complicated but VERY useful to those "big sites". I have a site with 100,000IP/day and that makes me very embarrassed to remove many nice plug-ins in order to make the cache working efficiently.
Thanks for your reviews of this advice.