I wish each post could be saved in the theme it was written under, so if you clicked on the permalink for each post, it would display in that theme – I expect you’ve have to save the formatting for the post in a “side-band” CSS file/folder for images.

Wouldn’t it be fun way to be able to do a sort of weblog wayback machine, though?  Instead of even the oldest of posts being re-formatted to display in the latest theme?

It’d need to be an option, of course – choice is king!