This implementation of you is great, but there are some important differences with having full query management functionality.
Your solutions is great because:
* It's very simple
* It has huge benefits for API and Special:Ask queries
While the thing I'm proposing
* Is complex
* Does not benefit the API and Special:Ask (since it would consciously ignore these to avoid doing not needed work)
But then again, it solves another problem then your change:
* it fixes the existing persistent MediaWiki cache for articles to get invalidated at the correct points
* and it persistently caches results for inline queries
So these two caching solutions can live happily next to each other. Once the new one has been implemented I suggest disabling the current one for inline queries, but keeping it for all the rest.
Jeroen De Dauw
Don't panic. Don't be evil.