Although IWP only supports Classic theme, I don't believe this would prevent users from viewing layouts that have another theme attached. Why don't you have a stripped down version of the solution to run on IWP? Simply delete all layouts you don't need and save under a different name.
my 2 cents . . .
I found the answer - it is possible to do as I wanted. My problem was that in my start up script, I had a custom dialog box, to tell me which privilege set I was using. However dialog boxes are not compatible with IWP - and that was causing the error. I removed the dialogue box and everything was fine.