What could be the value of having a business analyst in a data science team?
I believe the integration of Business Analyst(s) into data science team makes great sense. 

For a number of reasons:


there will be a lot of interaction between business proper and the data science team. BAs are used to acting as an interface layer between IT and business functions. This is much harder than it seems, as IT and (for example) Sales &amp; Marketing people are by nature extremely different. It takes a lot of patience and experience to get them both on the same page. Hint: when talking to Sales or Accounting do not start with an icebreak about the virtues of Open Source!
BAs usually have better domain knowledge than DSs. They can be of great help in initial phases of the project as they tend to have a more natural "feeling" for the business (e.g. which outcomes are possible, and which not, are we forecasting a rare event and some under/over sampling is in order, what sort of results are no news and what kind are so surprising that they should be brought to board attention immediately etc.). Data Science types are good at finding the correct answers once a problem is formulated, but asking the right question is arguably more important. And it is a task a BA can help with.
Business Analysis is around for longer, so there is a deep and broad pool of experienced people around. Data Science is young but sexy and looks nice in a resume, so it will be easy to persuade a smart guy/gal with strong understanding of the underlying business and good relationship with the key players in the company to become a project member. It is a win win situation.