I think Karl_Brogger has made some good suggestions - finer hulls, T foils (rudders), and a specialized mast-sail combination for the uni config.

I thought the new A cat fore-aft flexible mast-powerful sail was partly for downwind trapezing. The spinnaker would change that. Rig is still a very important issue and a single-hander can use a more flexible mast.

The one foot wider boat comment could be most easily addressed with allowing beam insert racks - mini versions of the H17 type and removable for 2 up sailing. Would require a rule change, but that is the route I would go....

Taller mast isn't needed, as Uni is advantaged in light wind and overpowered in higher winds. More leverage, wider boat or wings would help there. Curved boards would be neat, but outside class rules and maybe hard for weekend sailors to get the benefit out of. I don't think self tacking jibs add much for a uni sailor, something more to adjust taking your concentration off the big issues. Lower weight is always good, but then you lose the 2 up, class compliant option.

Just thinking "out loud", what I think you wanted.