I'll play.
First, I want them to remake the Walch Navy .36 as a modern weapon: A twelve-shot (in one cylinder) double-action revolver chambered in .357 and available in varied barrel lengths. Frankly, I don't think it can be done since I'm pretty sure the pressure of a .357 is a lot higher than the old .36 loads were (also, the Walch was a cap-and-ball gun), so unless they can make a really strong alloy for the cylinder it would have to be comically oversize. Not sure how to handle the firing pin either, since the nipples for the percussion caps were, I think, smaller than the rear of a modern cartridge would be, and also firing pin vs. hammer impact... it would take a lot of redesigning, maybe two firing pins, I don't know. I would like it to work with a single trigger, but if it takes two triggers I'll still take one.
Okay, it would probably end up combining all the worst features of autos and revolvers into one prohibitively expensive, hideous-looking, over-complicated abortion: Sacrificing reliability for more rounds (and still falling short of an auto), without the rapid reloading of an auto magazine or the balanced elegance of a revolver. Still, it'd be a pretty neat little abomination, a firearm version of the Spruce Goose. It would be the kind of thing that shows up in a book titled "A History of Weird Firearms" 100 years from now with an author's note saying "Like Icarus, they dreamed great dreams, but flew too close to the sun."
...and I've been racking my brain to conceive of an automatic pistol that I want made. All I can come up with is modularity, but the Sig P250 did that. Maybe they could do it cheaper and with more caliber and size options, but honestly I'm pretty impressed by it as is. If they could make it DA/SA instead of DAO I'd be even more impressed.
