HTML is so sloppy that automated conversion from HTML to anything is pratially impossible.
Actually, it would be easier to translate from WML to HTML.
One of the best ways to handle the need for both WML and HTML generation is to use a development system which decouples the view from the model. Two of the most popular are Cocoon and JSF. Struts can be used as well, although it's slightly more work.
A lot of modern-day cell phones have "real" web browsers in them, so they don't use WML, they use HTML, and the only difference is that you have to present the page formatted to be friendly to a smaller display area, since cell phones are more likely to support 320x240 than 1600x1200 pixels.
You should also avoid using plug-in technology for mobile web pages. Many mobile devices don't support Flash, for example.
Sometimes the only way things ever got fixed is because people became uncomfortable.