I am sure I will get some flak from this, since I know a lot of people here have a low opinion of ranch dressing, even though it is very popular with the general public, but:

How about a blend of ranch dressing, a little sweet pickle juice (or maybe pickle relish), and a little horseradish sauce (just enough so you can just barely taste it)?  This would give you components of salty, sweet, and tart as well as a little “kick” from the horseradish.  You could also add something for a little “heat” (Tabasco, chipolte, etc.) if you thought your customers would enjoy that.

I have added ranch dressing as a “hidden ingredient” in several  different things where people have commented about how much better they tasted than the version they were used to.