Warning: about to get philosophical. Don't base your life decisions on what you think will get you into business school in the future. Do what you're passionate about. Do what makes sense for you in the present.
In my senior year of undergrad I was pretty darn positive that I never wanted to step foot inside a classroom again. Now I've been accepted to four awesome business schools.
If you make decisions based on what you think the HBS adcom wants to see on your resume, you are setting yourself up for disappointment. The backgrounds of people coming into business school are incredibly diverse. Honestly, the more you try to tailor your resume to the "traditional" business school background, the more fierce your competition will be when you apply.
Work where you want to work. Don't try to make a switch to IB because you think it will get you into a top business school. Do it because it's what you're interested in and passionate about.
I'm not trying to rip on you by saying all this. You are thinking the exact same things that so many of your classmates around the country are thinking. So I guess my advice is this: planning for your future is smart, but don't let a potential business school application make the biggest decisions of your life for you.