I'd welcome these dances, come to think of it, as a replacement of the Swingathon that sometimes crops up; maybe Week 11, just before real 2 dance week, the couples could do 1 full, normal dance, and 1 45/60 second new dance (Contemporary, Swing, Hip Hop, Bollywood, Jazz, Disco), which'd get an overall score from the judges as a consensus (1 through to 10).
So it'd be like:
Couple A: Waltz 39, Disco 8, Total 47/50
Couple B: Samba 38, Jazz 9, Total 47/50
Couple C: Charleston 38, Contemporary 8, Total 46/50
Couple D: Rumba 34, Swing 10, Total 44/50
Couple E: Quickstep 35, Bollywood 7, Total 42/50
Couple F: Argentine Tango 31, Hip Hop 6, Total 37/50