{dynamic}/{insert} and caching

Ever consider adding a {dynamic} template function or extending {insert} as a block function? The intent is that anything in between wouldn't be cached. Plus you wouldn't need to create a custom function for {insert} (and probably a separate template as a nicety for the text that function returns). Or add a "file" attribute to {insert}... Would creating such as custom block function even be feasible with smarty currently? Browsing through the archives, it appears assign() can be used to override vars in cached templates (haven't tried yet). Gerard