After a few months of trying to make reset CSS work, the answer is: just use the &$^* iframe.
There are just too many potential problems and pitfalls, from balancing reset's class precedence to the fact that any CSS will just roll over legacy color / positioning attributes (which are still relevant in email authoring).
iframe
is a headache to integrate into the page, but at least you know it can be done, and once it is done, it stays done.