Yeah, I agree, which is why I only think in terms of small things. Like poop filtering.

Afaik it canonically can. We've had people rebuilt from the buffer, so it literally has done most of those things. The downside to most of those is that you would lose your memories of everything that happened since you were last scanned. Also, it's illegal to rebuild people from buffer. Also, the body is implied to be so complex that you can't just edit one, like curing their cancer. You have to rely on a scam, so you would need a scam of that person without cancer. For simpler things, you can just edit them without needing an original scan, and that's how their food makers things I can't remember the name of work. It's literally the exact same tech as the transporter.

Given the explanation of how it works, it just vaporises you and constructs a copy elsewhere.

diseases: it does. they mention this numerous times over the years.

wounds: tricky to differentiate between body modifications and scars (for example). safer to go to a doctor than rely on a computer.

immortality: same thing, basically.