I haven't done it personally but that's mostly because I don't really enjoy beer cocktails. But the flavor profile would likely match well with many styles.
You could do it by adding alcohol, but then you do wind up with a beer cocktail that has a burn to it.
You could use the same raw ingredients (molasses, dark unrefined sugar) in your beer and get a similar profile. Some of the darker (D, D2) Belgian candi sugar syrups will give you those flavors.
You could take a page from cooking and flame the alcohol before using it. That should preserve most of the flavor while removing a good portion of the alcohol. Heat the alcohol in a shallow pan and then light it with a butane kitchen lighter or fireplace match. Leave it alone and let it burn off, then use the resulting liquid. It will still have some alcohol in it, but less. Cool it down and taste it and see if you like the profile.
Whichever approach you use, I'd also recommend that you start by blending an existing batch with whatever you want to use on a small scale (like a tasting glass). This will give you an idea if it's a bad idea or not, and will let you see what proportion you like. If you come up with something that works, let us know.