A gentle sweep for a good clean cable, well adjusted spring tension, no graunching on the pushrod or operating arm at the gearbox, no burrs on the clutch drum or the tangs and notches on the plates is what you can do, short of increasing the length of the operating arm to gain mechanical advantage (which demands bigger hands!).
7/8th" between-centres 'bar levers will help a very surprising amount (if yours are an inch or more).
A modern Enduro-style lever at the 'bars would also probably help but look terrible.
A bearing in the pressure plate might make things smoother and feel better, but not necessarily lighter.
Been trying to find a reference to or pic of a quite neat 'mid-point secondary lever' system that does / did exist but I can't find what I was looking for. It's out there somewhere, but maybe wasn't a commercially available gizmo. Idea was to make the cable a two-stage affair. First section ran to a fixed pivot with unequal length arms either side, second section from there to clutch operating lever. Relative length each side of fulcrum determining the scale of the improvement. Never had one, not sure of effect on hand size, but do recall people saying 'transformative'.
Maybe someone else here has one or can find an example out there somewhere.
