Cheese Cake as a filling?

It should work fine as far as I can guess. I have used a white chocolate/cream cheese frosting/filling with chocolate cake before. It is similar to the cream cheese icing you would use with carrot cake but with the addition of melted white chocolate...you need to melt the white chocolate over a double boiler, cool to room temp and the icing should be at about the same temp when you add the chocolate to it. If the cream cheese is too cold, the chocolate will sieze up when you add it.

Sure you can use cheesecake as a filling!!

It seems too much work to bake a cheesecake, only to mash it up and use it as a filling, which is why a cream cheese icing makes more sense. Alternatively, you can bake a thin cheesecake, freze it, and use it as a layer between two choc. cakes, without smooshing it up.

Yep, that's the way I like to do it. I use a cheesecake layer between 2 flourless chocolate cake layers (then pour ganache over it) for one of my cakes and it works great. My cake is heavy and dense but I'm sure it would work just as well with any type of cake.