A closer link to NATO can help build up this common sense of purpose and calm things at home. Much of the current tension in Bosnia exists because all parties feel insecure about the future structure of the Bosnian state and their status within it. Having a MAP with NATO can give all sides a sense of security, making them more confident about undertaking necessary institutional changes, even when politically difficult.
The ethnic divide in Bosnia has been stubborn and on my last trip to the region I saw little sign that Serbs and Croats were more reconciled to a unitary state. But I have no doubt that working out that dilemma in the embrace of the EU and NATO is far better than Bosnia doing so on its own.