sorry rdcast, i, like most people, like a nice dense cheesecake and have never tried to make a light, fluffy one. however, as an ex-chef of over 15 years experience, i can virtually
assure you that if you aerate your cream cheese well and are careful not to overwhip the eggs, you should have no problems getting the light (for a cheesecake) results you want.
that said, the sour cream and ricotta will be detracting from the lightness. i also think you could ease up on the flour; most recipes do with just a few tablespoons. however, now we're talking about how i
would like a cheesecake. also, we are talking about cheescake: it'll never approach the consistency of say, italian meringue. that said, i think you can safely go for it.
also, anyone who would try using baking powder in cheese is obviously open to experimentation, so...
entering the world of wild speculation, you might try coming at this from another approach. a creamcheese cake. start off with a geniose or sponge cake batter and then fold in well-beaten creamcheese that has been further aerified with some softly whipped egg whites folded in. you'd probably have to settle for a more shallow cake, but the results might be good. you'll never know unless you try!