One problem we have around here is it is quite nice and warm in the sun (75 to 80 deg in the winter) but the water can be 65. ...
This is just my opinion about dry suits, but on a nice winter sailing day in the high 70's if all zipped up I would think I would get very warm, so one would tend to open the dry suit up. Since you never know when trouble will happen my perception is if you went into the water with an open dry suit on it would fill with water, and be very difficult if not impossible to get back into the boat, and of course once it's filled with water I would assume it to be worse than nothing at all. Thats why I went with the layered approach, and everything can easily be put on in the water if needed.
Ahh, the balmy sun in Florida. That sounds like a typical summer day in the inland Northwest on the water (not during a heat wave), and hotter than most any summer day west of the mountains on salt water. So I agree completely with your thoughts about dry suits. You could knock 10 degrees off those air temps and a dry suit with even a moderate amount of insulation under it would create a heat stroke problem if the sun is out. And you'd want a bit of insulation under it for 65 degree water. I also agree that a dry suit with an open zipper is like the proverbial screen door in a submarine.
I'm curious about the need for gloves at those temps, but gloves are a pretty personal thing. I tend to get cold easily, but for some reason I don't start wishing for gloves until the air temp is in the mid 50's. When I do wear gloves I like a pair of well oiled light weight leather gloves. They will be soaked in a few minutes -- but ever so flexible and comfortable and easier to work with and put on and take off compared to neoprene kayaker's gloves. And I find them warm into the 40's (air) anything colder and I stay home.
I'm also curious why so many people like wet suits. But again, I know that a lot of personal taste and personal metabolism affect our clothing choices for water sports. I bought a farmer john about 20 years ago -- tried it a lot and never liked it. Even in 50 or 55 degree air temps with the sun out, I feel like I'm roasting on a spit. Then I tried swimming in it in 65 degree water. After 30 minutes I still felt like I only had swimming trunks on -- with serious shivering taking control. I wonder if my rather thin body frame does not adequately fill up the space. So fresh cold water just keeps coming. Never thought of waiting till I fell in to put it on. But I can't imagine spending time and energy dressing in the water rather than getting back in the boat pronto.
Enjoy that Florida winter!