How to earn a Bachelor or Master without attendance?
It is already possible to do that to some extent in many US universities, these are called majors and minors, in your case it would be having multiple majors. Yes you can use the same credits for different degrees but there are only a limited amount of overlapping credits in our related fields. Additionally, I think it will be more complicated to have majors across colleges. Bottom line is that you can only "reuse" a limited amount of credits, so you will still have to take many exams to get the additional credits, regardless of whether attendance is required or not, because you also have distance learning that doesn't require attendance.