yeah, i mix everything in together and if it tastes good, then thats great! i don't really go with any food rules (probably cos i don't know them, lol).
my spagetti and pasta ends up with anything and everything in it, in assorted combinations, including kidneybeans, butterbeans, borletti beans, 6 bean mix, teeny tiny homemade falafels, leftover nutloaf/nutburgers rolled into meatballs, corn, french beans and broccolli, baby tomato wedges, pan fried zuccinni slices and garlic, chunks/crumbles of soy protein or real veggie based vegeburgers, sliced tofu sausages, tofu burgers, etc etc etc.
basically whatever is lying around, and tastes nice, goes in there- same with any food, not just pasta! stops it getting boring, and ups the veggie/protein content too!
throw it all in there, go on, go for it..... rebel!