If limited by budget, like most on here, I would get estimates for #2 & #3. That most likely will tell you what you can or can't do. I agree with anthropic and would go for #3 if I could afford it. I'm also a pond owner in Iowa and a 5' deep pond with a lot of weeds is not good here. Some years I will have close to 2' of ice on my pond, so it would be very difficult for fish to make it through the winters here in a shallow pond like yours, especially if you have a weed problem.