Not sure why you wouldn’t want your Business Analyst be part of your team.
Though I do not know what solutions you are developing, a Business Analyst role can be hugely helpful in:
* informing process and workflow aspects for your products and services
* helping to define check points, KPIs, required measurements etc.
* assessing dependencies to legacy systems & possible migration paths from existing systems
Agile development does not mean you let everybody in your team or project go on the loose. You will need somebody who can reign people back in where they go over board or come up with solutions that are detrimental to your wider business. Agile development shouldn’t live in isolation with your other activities, products and work streams.
If you have a capable Business Analyst he/she might fill that role of providing the necessary boundaries and help your agile team to move forward in a way that is consistent across your business. You may even consider deploying your Business Analyst in a role that provides some best practice and common approaches across different agile teams.