The Colt's thumb latch is also the recoil shield, and it works in the opposite direction of the Smith latch. Reengineering the thumb latch, while not impossible, would have been quite an undertaking. The client owns a number of Pythons and wanted a revolver that looked like a Python but had the reliability (or lack of fragility) and action of the Smith.
Impressive, but what about that thumb-cylinder release, I would have gone all the way and fashioned one to look like the shape on a Colt.
With all that labor and expensive machining, I would imagine it would have been cheaper to buy a real Python in tip-top condition.