I'm not proposing to work on individual elements, but on all of them. But I understand you point of view.
Would you accept this as input filter (i.e. ODT in specific) option? Sorry, but I have to ask before I do it as a wrapper. I promise this is my last try
But...
While thinking about this, I thought about plugins. But there is currently no way you can put a conversion plugin between input and output (in the plumber). This would open up the architecture for all sorts of markup and style optimization, while keeping the core functionality of Calibre clean. But obviously this would be much more work.