Recently I've been spending Sundays playing with something new. Here's today's results.
In the first case I've setup overlays so that when you click on a cufon rendered block of text you it transforms into the unrendered version until you click elsewhere. In the second experiment you can select and copy but you don't see your highlighting.
Both of these are just experiments and certainly not complete solutions (and they've only been tested in firefox). But perhaps they will give someone the inspiration to come up with a complete solution.