I too think that Mason's best position is more forward. The problem is that there's no one to play the position he's currently playing and I don't see him displacing our existing forward options. Many people have said Eriksen should play deeper, but he doesn't have the strength or defensive ability that would also be needed in that position. So switching Eriksen and Mason is not an option. However, it would be interesting to see Mason at the top of the diamond in a 4-2-1-2-1 formation. Another option would be to play him in the 10 spot and move Eriksen to the right (with Chadli staying on the left). And if all this sounds like I'm making stuff up, it's because I am!
But gosh darn it, I like the guy and I think he's a very good player and would like to see us taking advantage of his best qualities.