I thought the whole point of squaddies was so you had someone you could laugh at after you shot them down and still be friends afterwards. 

I say this like I could actually shoot down anyone else in my squad, but I rather like the theory. 

More to the point restricting side switching I think causes more problem scenarios than it solves.  I used to fly pretty much knights exclusively, not that I cared what other people did but that's where my "friends" were.  When I did start hoping around I discovered a lot more people out there who were a lot of fun to fly along with or chat to.  The benefits of side changing simply outweigh the "problems" as I see it.