Mark Hamill on Twitter reveals his idea for Boba Fett in the original trilogy:
I once suggested it to George as the only way we could top Vader being my father. I envisioned her as a double-agent working clandestinely for the Rebels.
Now, Ben Pearson writing for /Film:
Watch all of Boba Fett’s scenes from the original trilogy thinking about “him” as a woman disguising her voice. It adds a different level of intimacy to all of the conversations between Fett and Vader (who, remember, would be lovers in this scenario).
I’m fascinated by this idea. Sure, at first it sounds a bit weird (and wouldn’t work with the prequels), but it provides Boba Fett with a way richer back story than the character currently has.