Yes it will work.

I use dogbones on my boat and have the setup you have drawn. In light airs you just pull the ring up to increase the tension in the bungee to get the trapeze line hang really straight. I prefer to lift myself up before going in, makes sliding over the hunwhale easier as well as getting out easier.

I'm using dyneema 3 mm high tensile line instead of wire and I only need a small amount of tension to have my trapeze line hang straight.

With dogbones you don't even need the little pully and shackle I just let the line run through the upper loop of the dogbone. That is low frictions enough.

When I get to my boat I will make a picture of it and send it to you Robi. This will take a week. The way I've done on it and that is very similar to what you have drawn results in the cheapest trapeze lines that are also the lightest while maintaining great adjustability.

Wouter