Here's an *existing* state regulation that arguably does burden a business owner's exercise of religion. In Indiana, sale of alcoholic beverages is prohibited on Sunday. Suppose I am an orthodox Jewish owner of a liquor store (or a chain of liquor stores), and my religion pretty much says I must be closed on the Sabbath--Saturday. Other liquor stores get to be open 6 days a week; I can only be open 5 days a week, if I "exercise" my religion. Sounds like a substantial burden to me. (One can do the same thing for almost any business owned by orthodox Jews, or Seventh Day Adventists, and so on. The liquor store example is telling, because it requires store closings on the Sabbath of a *particular set of religions.*)
Feel free to propose other plausible examples that do not include discrimination against a *class of customers* in comments. I will delete any comment that proposes discrimination against a class of customers.