The ability to exchange the Emblem and bluffems between teammates is a great idea. However, instead of being a completely free action, I think it should be a quick cast spell that costs 2 mana and has a range of 0-1. Here's why.
Thematically: if the emblem could be exchanged that easily just by handing it to them, why doesn't it get blown away in a sandstorm, or knocked off when its mage is slammed into a wall? I'm thinking the reason for this is that the emblem is tied to its bearer magically. Also, they need their hands free for certain kinds of equipment to be cast on them.
Mechanically: if it was a completely free action that didn't require anything other than being in the same zone, then winning players would probably stake out one spot and stay there together the entire game, constantly switching the emblem holder, while sending out other creatures to take the enemy's flag. While this turtle+swarm strategy is still a good one to use, I don't want it to be the one go-to strategy like it is in the real-life gymnasium version of capture the flag.
Also, I'm thinking that each team will start in an opposite corner of a 3x5 zone board.
For distinguishing Emblems and bluffems from enchantments, I was thinking that they should just have different card sleeves.