The five schools function like one big campus, in many ways. They share a common registration system, so signing up for Mudd or Pomona or Pitzer or Scripps classes, as a CMC student, works exactly the same as signing up for CMC classes, and students mingle freely, eat at dining halls on any campus, participate in joint EC’s, etc. It’s true that the undergrad major would be econ or econ/accounting, but the School of Econ & Finance is very business-y and also offers a BA/MA Scholars Program that allow students to complete an MA in Finance within the 4 years. (Although this “requires significant advanced planning” and would probably preclude completing a full CS major in the same timeframe.) You might find that it doesn’t fit as well as some others, but the course offerings are there in all areas of interest and the financial aid is pretty generous, so it could be worth a look.
You might also check out Trinity U in San Antonio. They meet full need and have both a finance major and a cs major, and their Pathways Curriculum is double-major-friendly. With a 28% acceptance rate, Trinity would fall into the “missing middle” of your list, that I alluded to - still competitive and generous with aid, but not in the single-digit acceptance rate category.