We also have a 515, she is a 2004. We have the same ideas. A couple of thoughts.
1. A hard cockpit cover would be ideal for all the reasons you suggest. Do you have a windshield? It would make a difference. Is your steering forward or aft? Ours is forward with an walkthru cockpit. Look at the design of your deck salon section. Imagine those same or similar lines carrier over the cockpit and then properly joined with the windshield (if you have one). I think if we’ll done, it could be gorgeous and practical. Needs good design and excellent fabrication in order to not destroy the 515’s beautiful lines.
2. If you like, I’d be open to approaching the Hydrovane company about a solution for our boats. I believe their weight limit is around 50K lbs. but they also suggest they can design a solution for almost any boat. I agree that having an autopilot and a vane makes sense. Hydrovane would be especially useful if steerage is lost. I hate the idea of driving from the owners stateroom. The Hydrovane provides a remedy to that issue.
If you like this dialogue let’s move to email, I can share some pics.
Excuse typos – using mobile phone.