The play I saw was, in fact, dramatized by Patricia Gray.
The notion that this increased the number of roles for females did occur to me. However, I think that of the 13 dwarves, 10 were played by actresses. They were duly packed up in many layers of dwarvish garb and thick eyebrows and plastic foreheads and beards, so it worked.
It was actually pretty entertaining on the whole, but there was just the one major error in this version: supposedly the dwarves know nothing about the Ring, and when faced with capture by the Elves, Thorin says, "Bilbo, put on your Ring" ... that I don't actually know about.
Ooooops.