I remind myself that what we are talking about is a very sketchy (in both senses of the word) description by @FStratford of something that is not yet public. I don’t mean to impugn his or her motives, but it’s not really clear what this is.
The OP described it as a huge departure from the existing world of Chicago education (and, in a sense, as a new model for undergraduate business education compared to Wharton, etc.). However, without too many tweaks I could imagine something which is essentially a re-branding of a curriculum that is available today on an informal basis, and probably taken by a substantial number of students:
Students in the College can already take up to six courses at Booth. Only four can count towards the 42-course degree requirement, but in my experience most students wind up taking 45-48 courses anyway, so it doesn’t matter much if you take two courses that don’t count. There is already a special program, mentioned by @JBStillFlying , that involves formal recognition of coursework at Booth. At least four core classes at Booth (the foundation courses in accounting, finance, marketing, and entrepreneurship) have enough undergraduates in them to support separate sections for undergraduates, and there may be others.
The Economics Department BA requirements are not all that burdensome – there is a core that consists of 9 basic courses, plus what amounts to four math classes beyond basic calculus (some or all of which are required or suggested for most non-humanities majors), plus four electives (one of which can be outside of Economics, such as another math course, and some of which may be Booth courses). A student arriving at Chicago with no exemption from any aspect of the Core could do the Core, major in Economics (with, say, two Booth classes applied towards the major elective requirements, and two other business-related electives in the department), take the four foundational courses at Booth (only two of which could count towards the 42-course BA requirement), and still have room for 5-9 additional electives within a 3-4 class per quarter schedule.
That’s today. I might be a little grumpy about it, but I couldn’t really have a problem with the College branding that curriculum as “Economics Specializing in Business” (colloquially, Business Economics), and promoting it as a more intellectual, more academically rigorous approach to business education. And basically, that would be right. I would like it less if they compromised the Economics core, or if they turned more of the available electives into required business courses, but a little cosmetic fiddling here and there (replacing one or two Econ core courses with undergraduate sections of Booth alternatives) wouldn’t be the end of Western Civilization. And, voila!, I have something that could be described as the OP described it, and isn’t really a change in anything but marketing strategy.