Tom - are you planning to add the current players username as a system variable / expression in the arcade plug-in?
It'd be great to be able to call it from within the game itself, so you could do stuff like label players/objects/ui etc with the player name itself.
Another use would be comparing current score to previous score, say for doing achievements like personal bast, or flashing your username in a list of top 10 / top 5.
And for testing purposes - it'd be cool if the user had the ability to make a game non-public - say for testing before sticking up on the arcade, that or a 'beta' flag, that prevented it showing on the main screen, and possibly deleted it after a fixed period.