And a new, revamped Challenger, Pete.
Same OD cylinder, but with thicker walls and a 25mm bore. Slight increase in all-up weight but with lighter internals, reducing recoil. A sturdier barrel hinge bolt, along the lines of the HW or LGV. The bolt on scope ramp (or machined dovetail, made easier by the thicker cylinder wall).
I never thought the trigger was too shabby, but a slight re-working would bring it bang up to date. Synthetic top hat and guide and a rear piston bearing would make it truly scrumptious.