Just my two cents!
so our out-dated system that we currently run reports out of (that hopefully we can replace by KoolReport) has a screen like this. I can't see that working well with the look we are going for on KoolReport, I kinda picture more like a "create what a pivot report will look like", for implementing it could be more like Order1 [dropdown choice] Order2 [dropdown choice] order3 [dropdown choice] and this would be the order of the Pivot dimensions "row".
I am so curious how you are going to make the inputs looks - popup, opening screen, no the same report screen?