I had three dalmation mollies living with 5 BST with no problems. Well other than the mollies eventually getting sick and dying but no behavioral conflicts.
Ya i have haad 2dalamation mollies, and 3BsT living together nothing happened just the mollies were already sick and died. so i got my BST still. They are communtiy fish so not problems
Black Skirts can work with livebearers; I had a school in with my platies, swordtails, and guppies.
Commercially bred mollies, especially black mollies, seem to do better with marine salt in their water, which Black Skirts don't like or need. For some reason black mollies are weaker than other molly strains, really susceptible to disease in freshwater.
In a nut shell:
Go ahead and try it, but I don't think you will have much luck keeping the mollies healthy.