How long?
Are you willing to constantly audition and perform (IF you’re one of the very few who are cast) for little or no money for several (maybe many) years to gain experience and establish your credentials? Are you or your parents able to continue to pay for private voice, movement, and acting lessons well after college? As well as headshots and reels? And audition travel and lodging? Would you live at home or NYC or LA. Will your parents fund your cost of living? Are you okay with tutoring, nannying, dog-walking, waiting tables etc… to pay rent. It can take 5 to 10 years to start to gain traction in the industry, if your talented and lucky.
Per your criteria, you can’t apply to the bigger name Broadway/Hollywood feeder schools like U. of Mich, CM, Juilliard and UNCSA, as they don’t allow time for double majors. Google their curriculum and you’ll understand why.
Alternatively, in a BA program like Williams you really need to aggressively supplement your course work with lots of extracurricular theater - very late nights and long days in sometimes erratic student productions. A BA program is typically not going to provide the consistent voice and dance training needed to immediately pursue a professional musical theater career. Will you have the time and resources for private dance and voice lessons during the academic year? Will you have the summers free and the resources to participate in summer intensive training? Is that compatiable with the research and physician shadowing seemingly required now days to become a competitive med school applicant? The standard now seems to be to take a post undergraduate year for MCATs, resume padding research and med school interviews. When would that happen for you?