"Kilt as jeans"? I have no problem with the concept. But sartorial ideas of what to wear with jeans, at home or privately, vs. out in public, may differ. Would I, or do I ever, wear an untucked t-shirt with jeans? Sure. At home. Never, ever out in public.

The absolutely most casual I'd ever get with a kilt in public -- on a very hot day -- would be something like this: