The long seat tube is a weak point on the Moulton. I had to reinforce mine.
Why not spread the top and down tubes where they meet the head? Then you could lose the oogli gusset.
The reason i haven't spread the head tube joint is because that would increase the angle of the top tube. I don't want to do that because 1-I don't like the look as well, and 2-it reduces the ease of step-through. I kind of like the look of the gussets, they add a couple more curves to the frame.
I see what you mean, but that will be a difficult junction to weld with 3 tubes and a gusset coming together in a small area. The top tube angle could stay the same if you made the seat stay angle more vertical and that would keep the seat post shorter, which as I mentioned, is a weak point.