You can put games in full screen: cache.armorgames.com/files/games/
Then add in the game name. If it has more than one word, then space each word with a - sign. Then put another - sign and put the number of the game beside it. Finish with .swf
Since not everyone knows how to do that, I agree with your idea. It'd be nice to have a button near the game saying "full screen", but some games look terrible in full screen, such as a few games where the screens are rather small; making it in full screen doesn't make a difference and makes everything in the game blurry.
Keep in mind that using GoM's suggestion may break some of the games which use our auto-login feature to access certain things about the game, such as premium content or access to the multiplayer server.
We'll have more games with full screen mode on AG3.