I feel like the original question is sort of being lost here. I'm am not a professional but love BBQ. So this is more from the point of view of someone who would be your customer who knows how to make his own but likes to find good Q.
I think if you make your own it gives you some increased level of credibility from the public. This doesn't mean you need to make six sauces. In fact you might just want to try to make what you would make for your own tastes and call that your signature sauce.
The other thing I would suggest (speaking as a consumer). I love to try new sauces. I get excited when I find one my local stores carrying a new product. You could also consider using a sauce that you can not get locally. For example where I live Blues Hog just doesn't exist. If I came up to your stand and you had sauce that I had heard about but couldn't get locally I might try your Q just to get a taste of the sauce (but maybe I'm strange). And finally some people don't want to put any sauce on that they don't already know what it is. So, if this is at all possible for you what I would suggest is to try to have one or two sauces that you make yourself (maybe your mustard base sauce and one other), one sauce that you bring in from another part of the country (say Big Butz for example) and one very basic sauce that people who are not very adventurous would use.
Take all that for what its worth (albeit maybe not that much). Overall good luck with your business and I hope I get to try it someday.
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