I worked as an accompaniest for dancers for 20 years. One approach is to get the rhythmic information from the dancers so that one is sort of underlining or shading what they're doing rather than providing a rigid grid ,different than the way drums and bass lay down groove in band situations .It's possible to get a really interesting feedback loop this way. It would be more difficult with looping,you'd have to ride the tap tempo constantly ,but it could be done. Another way is to do texture instead of groove ,and to sort of do dynamic counterpoint,contrasting the empty spaces to make them stand ou more,sort of, draping or framing the stage with audio texture . I must say that it's also entirely possible that you're giving someone the impression that you're going to take the spotlight and they're trying to put you in your place. I've often thought dancer's have the most fragile egos of all artists-but then I think of working backstage with a particular English rockstar guitarist who was the bitchiest person I ever encountered- then there were this actor in LA...... Unfortunatley many dancers and many musicians haven't actually experienced what happens when you really get entrainment between dancers and players. a kind of dynamic dialogue that's a really incredible thing,whole cultures have been based on it.