Converting business unit to different ledger group

We have a company that we do not currently own controlling interest in. Therefore, when it was setup, we decided to put it in a separate ledger group/ledger to keep everything segregated. We also use separate books for AM and a separate bank account for AP. We are now getting ready to buy controlling interest and are trying to determine the best method to roll this business unit into our main ledger group, AM books and bank account. Has anyone experienced this situation? We are trying to determine if we should change the existing business unit or if we need to create a new business unit. Seems like there are pros and cons on both sides.

Thanks!

Alicia, my only reason for creating a new BU would be to totally separate this business and then when you roll up all the BU's into your main ledger group you would always know where these amounts came from. It may be more work but worth it in the long run.