The big problem with thickening the sauce is that, no matter how thick it gets, hot cheese melts, and liquid doesn't hold stuff together that well. I'd need to add either starch or gluten, and that'd just mess with flavor and texture.

I tried to find smaller pasta, but I still wanted something elbow-ish, for the mac&cheese look. I thought about orzo, but for this I just wanted at least semi-traditional.

The plastic wrap/chill/slice/heat was exactly what I did. The recipe isn't perfect, mostly because pasta isn't quite as sticky as sushi rice, but it's fun enough that I'm glad I tried it.... :)