BBA+MBA is at least 4/5 years commitment, and this is also a phase where studeynt often change their career plan. In your case, if your goal is set, that what you would like to be after study, then you can consider this dual degree path. But, i would choose other prospects, if I had to make decision on it.
I believe BBA is half cover/repeated in MBA. I would say more than half. Because, many students who pursue MBA, they never studied BBA in the first place so things get repeat for them. Importance is given to MBA over BBA in industry. Person studying MBA would go through entrance, expected to be mature adult than young BBA student. (Industry Perspective)
I am of the opinion that you should invest your time with discretion.
Employers are changing their mindsets and now their demand is beyond degrees. They need right skill sets, performing employee and employee with Entrepreneurial Spirit, with good team work prepradness and interpersonal abilities.
Putting that in to a perspective, courses will change. For example, MS in Finance, Master of International Business, MS in Organizatioal Psychology and so on would replace traditional MBA.
Be strategic when you make career decision. You need a plan and to make a plan you need to do research and analysis of opportunities, scope and your own personality to choose the correct path.
Course like BA in Psychology with MBA, BCA with MBA, B Com with MBA etc., Will get more demand than BBA+MBA except skills and performance potential is proven.
Obviously, employer will give preference to a candidate having wide and diverse knowledge in multiple domain with one specializations.
Hope you got the answer.