Have you considered what you actually want to do with your career? While the MBB are known to be fantastic places to start a career, there's a whole wide world of consulting firms out there to consider. If you can land an MBB role that's excellent, but before signing yourself up to tens of thousand in additional debt trying to increase a tiny chance of MBB to a small chance of MBB, you really should be making sure there's an actual reason you want to be there specifically.
Contrary to the idealistic view many students have of the MBB, they really aren't some mythic otherworldly firms where you run around making "strategies" (buzz word 101) for fortune 500s daily on your grad scheme. If that's the picture you have in mind then I seriously suggest doing your research before betting 30k and a year of your life on a shot at getting in. In practice it's not that unusual to find MBB consultants working alongside Big 4 (& similar) consultants at big clients - often enough it's the same job but with a more prestigious brand name.