All your points are solid, I just think the comment that PCC's just "increase hit probability and shootability inside of pistol ranges" doesn't reflect on the experiences of many who I know have run them. Even the pseudo-SBR pistols being used with much shorter barrels and sight radius (although almost all run some form of RDS optic), actually stretch their potential from 50 to 100 meters. I find I can run a course with a PCC/pistol and I'm far more accurate, faster on target with extremely more efficient with follow-up shots than I could every imagine with a handgun...there's really no comparison. I've stretched traditional 16" barrel PCC's out to 150 meters, which for me is the maximum distance I'm comfortable with; however, most dynamic range training is inside 100 meters, which I think is perfectly suitable for PCCs.
For me, these stretch your pistol range from 50-100 meters, while increasing hit probability, accuracy, and rapidly getting more rounds on target much faster. Having borrowed/run and seen the MP7 and the CZ Scorpion SMG's used on the range here in Afghanistan, I see zero comparison of something this size with a handgun, especially when engaging multiple targets while moving with ranges out to 100 meters (didn't even use full-auto; single shots or controlled pairs). I will eventual SBR a few of my PCCs simply due to size efficiency and performance inside that 100 meter range. Agreed that they are not a replacement for a rifle caliber carbine/rifle, nor are they a replacement for CCW. Very much a niche firearm, but they fill that niche extremely well.
ROCK6