If you interest is in stage design, try "How did the proscenium stage allow the wing-and drop set?"
If your interest is in the social aspect, try: "When theatre became indoors, how did the community experience of going to the theatre change?" (Orange wenches, servant saving seats for the upper class, etc.)
If you are interested in the literature, try: "How did the physical theatre configuration change the dramatic content of the plays?"
Part of the "fun" of finding a thesis statement is focusing on your special area of interest.
You might try an essay on Japanese Theatre.
Why did the the role of onnagata come into being in the Kabuki Theatre?
Of all historical events from which the Japanese theatre takes inspiration for its plays none is more important than the Gempei Wars (1180-85) -- the death struggle between the Heike and Genji Clans for control of Japan.
The use of the hannamichi in the Kabuki Theatre breaks through the proscenium in a way that makes kabuki even more intimate than Western Theatre.
Far from being the 'museum theatre' it is thought of today, during World War Two the Kabuki Theatre was alive with new plays, engaged in dealing with the war and contemporary issues of the day.
Just a few random thoughts.
For sources see:
The Kabuki Theatre by Earl Ernst
Theatre East & West by Leonard Pronko
Kabuki's Forgotten War by James R Brandon
Traditional Japanese Theatre edited by Karen Brazell