MBC takes .CSV files containing the data. If you add new respondents and make the .CSV files larger, then you need to re-run your models again to get new HB runs. That's because in HB, each respondent's utilities are derived using the total sample of respondents. Your model setup (where you pick which independent variables should be included for each dependent variable) should not disappear when you modify your .CSV file to add new respondents. Just re-run all your existing HB runs after you have modified your .CSV file to include more respondents.