just by the nature of the biz, the "lookalike" part of it would be secondary to what happened once the date started.  I mean, it is one thing to see a Cher lokalike singing songs and sounding/looking like Cher.  However, once you got past the Kournakova looks on the gal, what would it matter, unless you were into role playing, and you wanted to act like you were doing AK, or whoever.  My guess is there wouldn't be a strong market for that.  

Now, if we had porn star lookalikes, they could continue on the role quite easily...