I can't reply as any kind of expert on sidecars but I can identify with your situation- the same one I'm faced with! It's either 3 wheels or forget ever getting my knees in the breeze again, thanks to physical limitations. To me that makes the decision simple and obvious!
Far as I know your bike is ideal for a hack tug. It has the power to handle any conditions you'd ever face and to haul any normal sidecar ever made. The car should be about 1/3 the weight of the total weight of the rig but that doesn't limit you at all. You could use most any chair and add semi-permanent or permanent ballast to get the numbers and the handling right, safe and enjoyable. Of course that ballast should be well secured in the sidecar as you don't want a weight shifting or sliding around! Best to keep the ballast in the triangle formed by the 3 wheels, and to the rear when possible.
There's some really beautiful sidecars out there that would be ideal on your bike, thumb through the Hack pictures thread, 'Hacks - let's see them' for some ideas. I've seen several big Goldwings not only handling a large sidecar but also pulling a trailer behind, so you're pretty much unlimited in making your dreams into reality! You can either mount the chair yourself or leave it to a professional, there's lots of info in this forum section on either decision.
I've decided to build my own because of limited finances but regardless of that I flat refuse to give up the freedom to get out there in the wind and RIDE! Nothing compares, you know that. The few drawbacks are minor and the learning curve isn't that steep at all. Many offer pro instruction on riding skills and sidecar specific technique, highy recommended for your safety, so that's another non-problem.
I think you'll be a whole lot happier with an outfit based on your Goldwing than sitting around with the channel changer wishing you had done it. If I got any 'facts' wrong I hope those with more knowledge will correct me. Enjoy life, that's the bottom line!