I created a new code plex project for setting default master page in Team Sites for SharePoint 2010. In Publishing sites, there will be a layouts or application page through which we can set a custom or another master page as a default master page. Unfortunately, this is missing in Team Sites. This is what this solution is all about. Read more about it at
https://sp2013masterpagesetterapp.codeplex.com/
https://sp2013masterpagesetterapp.codeplex.com/