sherppa
At present the latch operates as rack and pinion with the driving part (rack)at the top. A lever system would have to work inverted with the pinion on the bottom.
The geometry of the lever would have to be such to operate between the trigger pin and the latch pin and shaped to allow your finger to go through the trigger guard.
Also the latch only moves about 1/8" to lock the barrel, the lever would need travel at least four times as much between the pins. But the lever could be notched to make up for extra travel.
A very precise drawing would be the first step to check on the feasibility.
The conversion would entail a complete new latch, a slot milled along side the trigger guard, a lever with some sort of retaining lock. The action cut outs for the existing thumb button should be fillet in. Perhaps it could be done by a guy with some moxy.
When the cardinal took Michial Angilo to the cathredral to show him where he wanted the mural, Michal Angilo said to him, Not on the f------g ceiling.
But he did the painting anyway on the ceiling.