Using something like US 41(I) would tell the motorist the class of highway (if they care), but in the US the Interstate shield has become a brand. Like it or not some companies use the presence of an Interstate as one criterion for locating a new facility. I would say what we need more is allowing certain well engineered non-freeways in less densely populated areas to be able to use the Interstate brand. For example, does all of future I-11 really need to be a full freeway? Maybe it does - I haven't driven that route, but I remember driving from Bullhead City, AZ to Las Vegas on US 95 - a pretty empty road. Is US 93 a lot busier?