@Macaronni-- hmmm... maybe... I would generally prefer to put in straight up vinegar in there (or Tabasco to get the needed vinegar content). If I wanted a tomato element, I'd also prefer to have grilled tomatoes than pure'd (ketchup) in there.
My mac and cheese rep:
1. Start by grilling chopped onions, ham (or bacon..), and cherry tomatoes in olive oil in a skillet. I might also throw in peas/carrots in there if I want extra veggies. If using chopped mushrooms, they also go in at this point.
2. once you got some grill marks on those veggies/ham, and the pork oil is mixing all nicely with the olive oil, put in some milk or cream
3. bring it to a boil before putting in the sauce packet
4. the noodles come in next
5. As things thicken a bit, you put in vinegar and more olive oil to loosen things up (and get that kick!); you also mix in seasonings such as Oregano, Red Chili Pepper flakes, and Black Pepper. If more salt is needed (probably not) u consider it at this point too. Chili powder is interesting...
6. Put it in a bowl, and top it off with Parmesean (or Gouda, lol) cheese, and maybe a shot of Tabasco
Oh~yeah~
Another cool thing to do with mac and cheese is to start with Canned Chili. Think about it-- Chili has ground beef, beans, and spice-- all things that go well with Mac & Cheese.
@Spaghetti-- while I wouldn't put Ketchup on finished Spaghetti (it's ok, but not optimal), it's something I would consider mixing into tomato sauce for a more asian-fusion spaghetti with shoyu.