Volkameriana, a hybrid between lemon and sour range, is a vigorous growing root stock. All vigorous growing root stocks produce fruit of lesser quality. Trifoliate is the root stock of choice for a Meiwa Kumquat. Volkameriana is OK for trees producing sour tasting fruits, but otherwise it produces poorer quality fruit. It also produces fruit with lesser quality juice. I certainly would not say that the fruit of your Meiwa will turn out to be bad fruit, just poorer in quality than if the tree was grafted upon trifoliate. You could certainly air layer layer, or graft onto a different rootstock, or do nothing. If your really concerned it might be easier to simply purchase a new tree growing on a trifoliate rootstock.