I've pretty much covered those points at length, and acknowledged that the cost would be great.
No, you've covered each of them by picking one specific parameter and examining it in isolation from all other pertinent parameters and then moving on to another parameter and doing the same for that one. And, when necessary, ignoring the actual cost and talking about non-issues.
...the cost would be great. How great? No clue. I mean, .32 brass already exists, though it would have to be cut to a novel length. .32 projectiles already exist in what I imagine is a multitude of lengths and weights. The pistol frames already exist, although new chamberings and barrels would need to be made. I'd say more than half the work is already done.
This has nothing to do with the real cost. Making the ammo is trivial. The cost is from the consumer standpoint--what does it cost me to choose to buy a gun in this caliber. Some are money costs, some are not. Costs like availability issues for ammunition and accessories. Costs like the expense for practice ammo. Costs like concerns about future support for the caliber. Stuff like that.
I figure, as others mentioned, the pistol weight/frame would have to be intermediate to .380 / 9mm; and pushing a projectile with a similar mass to .380 at 10-15% higher speeds... well that would mean slightly more recoil, but perhaps mitigated by the slightly heavier frame and/or slightly longer barrel compared to .380.
If you can manage that, the controllability will be very similar to the .380 and you'll have a larger gun than the .380. Now instead of having a cartridge that is competing with the .32ACP--which might make sense to some folks, you have a cartridge that will be competing with the 9mm (bigger pistol and a more powerful round than the .380ACP) --which just isn't going to work if the only benefit is a gun that is only very slightly smaller and holds one more round in a single stack or two more in a double-stack.
The gun will have to be smaller than a .380 with at least equal ballistics. If it is bigger than, or the same size as a .380 then one more round in a single stack won't, IMO, be enough to make it sell.
Given comparable performance, I think it only has to equal the .380 in terms of ammo costs and availability (admittedly the hardest part), and people [particularly the 90%+ of people out there who do not yet own a pocket firearm] would choose it every time.
Well, the 90% of people who don't own a pocket firearm aren't in that boat because there are no options. There are lots of options. And I think your statement is very optimistic. Future support is a major concern, for one thing. Also, the only thing it's got going for it compared to the .380 is a small difference in grip length--if you can keep the other dimensions and the weight below or equal to the .380ACP which is questionable and probably contradictory to your improved controllability requirement. That's a lot of ifs and some serious concerns.
Regardless of all your legitimate misgivings, there is a 'hole' in the small pocket pistol world that needs to be filled.
Regardless of your repetition, the number of people besides you who agree with this statement does not appear to be significant. So far the market hasn't been actively looking for ways to fill the gap between the .32ACP and .380ACP. That doesn't mean nobody at all has tried--but when people did, no one was especially interested. Now, one could argue that if someone could come up with a semi-auto handgun cartridge that offers .32ACP capacity, handgun size smaller or no bigger than .380ACP and .380ACP or better performance that would generate some interest--and I tend to agree. I think that there is room for a cartridge like that--if it can be designed. I don't know if there would be enough interest to make it viable--but there might be.
I think it would be a home-run if a couple big names got behind it, and I think the technical feasibility is assured at this point.
Maybe, and not by a long shot. Cartridges with big names behind them fail on a regular basis--look at the .45GAP. And the technical feasibility is nowhere near assured.
Well, that's why it's a goal to keep it no longer than a 9mm, if possible. This is where testing would be needed.
Nobody, I mean NOBODY is going to want this cartridge as a conversion barrel/conversion kit alternative to shooting 9mm. 9mm is already the cheapest centerfire handgun round on the market and a fun/easy round to shoot--why would anyone want to pay to shoot more expensive ammo in their 9mm pistol?
I assumed you meant conversions to shoot it in .32ACP or .380ACP which would be problematic given the higher pressure and longer case length that would be required to meet the other design parameters.
I don't know how to say this nicely. The fact that you have given this a lot of thought and believe it is a good idea doesn't mean that it is actually a good idea. There are some aspects of it that could have merit--it will take a lot of work to determine if that is true--but there are many aspects which need to be re-evaluated in the light of basic theory of operation of semi-auto handguns and cartridge design.