>> [Complicate the browser design]
Are already coded, complete, and installed on 90+% of the desktops out there. <<
What do you mean by 90+%? 90+% of *all desktops* with browsers? So you have to emulate on the other 10 percent?
Yes, 90% of all desktops run either Internet Explorer or Mozilla, or some other DOM/Javascript capable browser.
The number of SCGUI platforms is...ummm...two. You and your buddy. That's it.