Put it into a secondary (before cold crashing-if you did not know) you can change up the flavors by repitching yeast, spice, fruit, sugars, converted starches etc. the sky is really the limit. You can give it a lot of character with caramelized sugars and spices if you are looking outside the box. Dry hopping is def a big option here and probably would be a recommended one, fruity spicy or floral hops would work with a dort. It just matters what you want to add to your beer.
A Dortmunder does not have fruit, it has a cornlike sweetness but no spices. So if you don't like the yeast quality in your beer, you can try and let it mellow out in a "secondary" with some corn sugar / dextrose, or cooked grits. Rice adjunct sugar whatever character you want to add to your beer. But remember when you are tasting what you have now it is un-carbonated and is not conditioned. Although there is high sulfites in this style, I for one am not crazy about adding any to my beer. But if you added something like fruit or spice you would be getting into a different style of beer. So Amstel Light is a dortmunder so is Sam Adams light and Heineken premium light all different tasting but still dorts.