A browser should support three formats: -x-, -vendor-, and the unprefixed version.

-x- support would be interchangeable with -vendor-, making -vendor- necessary only when the syntax differs for the vendor (gradients being the poster child here). So for almost every property, it would only be necessary to specify -x-property: 5px; property: 5px; If Firefox’s support differed, you would add the appropriate -moz- property (probably first, so that -x- could supersede it when Firefox catches up.

Since -x- doesn’t exist, this might be more of a “going forward” fix rather than cleaning up anybody’s current mess. For this to really work, it would be important to un-prefix as many current properties as possible (and be faster about un-prefixing new ones as they come along). That way, -x- would really be for newer, experimental properties.

I wanted to make a comment, but kept thinking of Remy Sharps post http://remysharp.com/2012/02/09/vendor-prefixes-about-to-go-south I think the section detailing Who’s guilty is telling.

Here’s hoping for the best

that once vendor extensions are implemented in other browsers we are stuck with them forever, just like the User Agent string

That’s a paraphrase, but it was a great example.

Therefore, it’s very difficult for a browser to implement properties found in another browser, even if it is open source. See how the .doc format took ages to be supported by Open Office (granted, Word is not open source).