Although not revolutionary, I could visualise this amalgam of Prosport / Airsporter / Whiscombe:-

Underlever recessed in the forend. Single cocking stroke. Highly efficient and refined 24mm bore. Secure barrel latch allowing safe direct to breech loading. All running on synthetic bearings and "factory tuned".

The loading procedure wouldn't be the quickest, admittedly, but this would combine some of the benefits of existing designs and the sleek looks of the Prosport / Airsporter designs.