Don't force a structure - not a significant issue if one branch appears to have more levels than the next.
I also am not usually a fan of the mix financial/non-financial. In my experience, often best to start with one (my go-to is a version of the business framework), before pivoting into the other (for me, usually the financial one). I highlight in the initial issue tree that I expect to execute this pivot at some point in the case, but dont actually describe it in detail until it is time to do so.
Many MBB cases will have you doing such a pivot at some point - I suggest you become familiar with that exercise.