I would make something like this:
http://southernfood.about.com/od/macaroniandcheeserecipes/r/bl20c1.htm
But with olive oil, instead of soybean oil, and dairy
not from a can.
If you want it to feel lighter, you want
less cheesiness, and
more fattiness. In a pan-based recipe, I would add olive oil, which feels lighter than butter, but it won't stay mixed in dairy, so I'd stick with butter for a crock pot recipe.
You can also add sour cream, and/or substitute the softer cheese with a soft fresh cheese, like ricotta.
Not related to heaviness, shredded green onion, bell pepper, chili, and garlic are hard to go wrong with in macaroni and cheese, along with various preparations of pork.