I'd love to see RangeInclusive fixed in the manner described. Part of what's blocking such a fix is that we have hard backwards compatibility guarantees. We'd have to do some kind of edition-based transition, where ranges start desugaring to a different type in a new edition than they did in the previous edition. We could do that, and there are various discussions going on to consider such approaches, but we're somewhat hesitant to go down that path.