Yes, you start playing the first match using the base game and expansions as explained in the first paragraph, then the alignment of the winning character decides which expansion the next match will be played on.

For example let's say an evil character wins the first game, the next one would be played in the harbinger expansion.

It's not a tournament, if it were, assuming there's one player per alignment, the number of expansions would only support a best of 3, meaning you'd have to leave out the sacred pool, dragons, spirit realm and cataclysm expansions.

This was just something i came up with because playing with every expansion on got boring after a while.

This is intriguing...can anyone tell me more about this? Looks like a set-up for a Tournament or series of loosely linked games?