completely understand the "time to implement" aspect as work leaves me with very little free time as well ... having said that. before you decide this is too difficult please check out the links below.
http://bf3stats.com/leaderboard/0orL9T75n02zDB6a2g
http://img834.imageshack.us/img834/4922/20120703044435am.png
you are correct. BF3stats does not track platoon stats. they do however allow you to create a leaderboard that tracks the stats of the members you add. these "lists" can then be made publicly accessible via a system provided URL.
having said that .... this function would require someone from the platoon to create a leaderboard on BF3 stats, manually add the members of their platoon and set it up to track ONLY the predetermined stats you (the developer) have predetermined. once this is done they would simply copy & past the url to this list into BBLOG. your server would then have to perform a simple "average" function for each of the columns.