I'm not sure it would necessarily make much of a difference (to how it is now; I didn't watch the early years). The judges are obviously quite capable of juding a tango, then a rhumba, then a waltz and so on, and I don't believe the vast majority of the voting public vote on the relative technical merits of the dancing anyway. Either they vote for the same celeb each week regardless of talent, or if they are floating voters, they vote for the dance they enjoyed best, not necessarily the most perfect. The judges might (should) pick up on small differences between seven (or more) consecutive tango's, say, and should score appropriatly, but to the vast majority of the watching public, they'll look damn near identical.