Sometimes people ask me a good substitute for certain plants, and while I'm not a powerhouse of native plant information, I'm learning. Usually when people ask about Crape Myrtles my go-to answer is Wax Myrtle.
Now I'm thinking I should add Hop Tree, American Plum, and Serviceberry to the recommendation list, depending on the drainage of the spot. None of these have the flowers of a Crape Myrtle, but the Crape Myrtles don't produce an edible crop for you, either.
To come up with a good substitute I try to match the multi-stemmed trunk and growth form and height. A good match would also have interesting bark and flowers, but sometimes you just can't have it all, and I think having an edible product far outweighs the flowers of the Crape Myrtle.
Hop Tree: The roots have the medicinal properties, but the fruit has an obvious, thanks to the common name, use as a substitute for brewing hops used in beer making. The fruit is also a source of food for wildlife. (images via Wikipedia and wildflower.org)
American Plum: Wild plum trees are thorny, winter-hardy, and thicket- forming, which means they're good for providing habitat for nesting critters. The edible fruit (which is what I think we "found" 2 years ago in our neighbor's yard overgrown and unused) is used to make preserves and jellies. The bark was used by Native Americans to treat skin abrasions and mouth ulcers. (my photo and one from the USDA Plants website)
Serviceberry (also a great substitute for Eleagnus): The sweet, juicy fruits are edible and rich in iron and copper. Native peoples dried the small pomes like raisins or mashed and dried them in cakes. According to the Wildman, "Iroquois women used the fruit as a blood remedy, to strengthen the body after the pain of childbirth. They drank a root and bark decoction to prevent miscarriage. They also used it to expel parasitic intestinal worms, as did the Chinese." (images here and the 2nd one now I can't find to credit. When I do, I'll update the link)
Wax Myrtle: Provide some protection from allelopathic plants when inter planted and accumulates atmospheric nitrogen on root nodes, similar to legumes. The olive-green foliage has a spicy fragrance, and Colonists separated the fruits waxy covering in boiling water to make fragrant-burning candles, a custom still followed in some countries The root bark was historically used medicinally as an astringent, antibiotic, and to stop diarrhea. See more information here. (both images from wildflower.org)