Well, you know the /execute command? Could you possibly add data tags to it? Like /execute [entity] [datatag] [x y z] [command] . With the datatag, we can run commands on specific mobs, rather than just using testfor. Although this is just an idea, this could be very useful to map makers. I was making an RPG so if the datatag was added, I could run a command on a player who has a specific chestplate equipped.

Also, this is a link to a forum with other people writing about this!
http://www.minecraftforum.net/topic/2404101-add-a-datatag-argument-to-the-execute-command/