What I do here is prep multicolor peppers-Green, Red and Yellow or Orange- optional with fresh chopped Vidalia onions (all I will serve). I do it to order and always clear the time (couple of minutes) with the customer first. Most of those folks also want the spicy mustard, and Gulden’s is very popular here, so I offer that. You could also grill a little kraut there at the end to just brown it and people will definitely be impressed. My customers love the grilled kraut, with or without peppers. I would offer it on a hot dog, but folks that like brats will get it this way more often.
Now you have a dish that tastes great, and looks great when served. I have to say, people are pretty impressed. But then again, I feel that the Midwest is under served by food cart offerings anyway so they are easily impressed. The East seems to be the place where it is really going on.
Hope this helps.