honestly you could try this yourself today. Grab a few emails, paste them into chatgpt, and ask it to write a system prompt that will write emails that mimic your style. Might be fun to see how it describes your style.

to address your larger point, I think AI-generated drafts written in my voice will be helpful for mundane, transaction emails, but not for important messages. Even simple questions like "what do you feel like doing for dinner tonight" could only be answered by me, and that's fine. If an AI can manage my inbox while I focus on the handful of messages that really need my time and attention that would be a huge win in my book.