I like the idea myself, especially with the achievement system in place. I like the idea of a fun little mini-game, like those mentioned, that would have in-game uses.

It doesn't really HAVE to be connected to other game-play. I just really enjoyed that aspect of FF8 (that the card game and game-play were connected.) But to be honest just having achievements associated with the game is enough for me. I was always a little dissapointed that they released Tetra Master as a separate game from FFXI. I always felt Tetra Master would have been a lot more interesting as a mini-game that you could do within FFXI.