Actually I'm not entirely sure that this violates a base principle, unless we _replace_ the command line interface for setting options, as opposed to simply augmenting it with an easier to use menu. If we augment, retail assets alone could still be customized as long as command line options are always available for any feature the new menu supports configuring (or at least those that make sense with only retail assets).
But here's the thing. Any HTML menu would exist to replace some menu that already exists hardcoded into the engine. Without some sort of existing new menu hardcoded into the engine for options configuration, how is a prettified HTML version supposed to even know what to do? We'd have to create the actual set of hooks and such for this new menu, allowed actions, etc, and if we go that far...we might as well template it out in wmcgui or an embedded HTML (I still think that's a viable option as long as this only augments command line, since those having performance issues can just not enter the HTML menu and load the chromium engine).