There's nothing wrong with the older green Pantins. As far as I can tell from inspection, they are identical castings (to the modern right-footed gold one).
Dr Storrick tried it once, found he couldn't use it [which is fair enough - it takes a good few actual caving trips to become halfway proficient with it], blamed the device & accused it of 'falling apart before I could climb three feet'. I'm not sure if accusing an ascender of detaching is quite the same as falling apart.
The CMI foot ascenders are crazy. We do not live in the 70s anymore, design and technology has moved on. I wouldn't swap my 80g Pantin for a 324g primitive hand jammer randomly lashed to my foot. And I wouldn't generally want a locking cam on my foot, in tight caves where I've left the Pantin bungee mod on too long I've had to kick myself in the ankle to get my foot free.
It's a bit boring living in a Petzl monoculture, but unless you're heading for something very specialist (such as the crazy Kong ultra lightweight ascenders), I believe you're better off benefiting from the decades of manufacture, economies of scale, ubiquitous availability and design refinement of the boring ol' Croll / Basic|Handed / Simple|Stop + Pantin.
Your D41 ascender for instance - all I see is a pre-80s Basic, before they added any of the ergonomic extras, & put in the mud flutes on the casting + cam. And it has a random extra bit of plating for no apparent reason.