Panic Button (1964) is kind of a grade-Z predecessor to The Producers. For reasons of his own, a sketchy businessman needs to produce a TV film pilot guaranteed to fail, so his son (Mike Connors of Mannix fame) hires an elderly Maurice Chevalier and Jayne Mansfield to play Romeo and Juliet. The plot ultimately backfires when the Venice Festival awards it a special comedy prize, and a network offers a lucrative 39-week contract for more of the same.
The balcony scene occurs around the 1:21 mark.
Anything close to Mansfield nudity?
No, but she was a very cute Juliet. I like her much more with a natural look rather than her familiar “blonde bombshell” appearance.