The sole virtue pistols have is that they are concealable. Palming is the skill for concealing things! 1, 3, and 4 all sound like good reasons to have a concealable weapon, and Longarms+Palming will do that for you better than Longarms+Pistols (albeit not as well as Longarms+Pistols+Palming). You can't want a concealable weapon but not actually want the ability to conceal it!
Also, I think you overestimate how hard the t-250 is to conceal. It's only machine pistol sized. You can stack up concealability modifiers: any of the loltrenchcoats are -2, chameleon coating is -4, and that gets you to a net of -4 which is plenty to hide it with a decent check.
2 is simply not true. In SR, carrying an assault rifle down the street is exactly as legal as openly wearing a pistol down the street - that is, if you have a license, it's OK. Also, cities are in fact full of "wildlife." This is this grimdark 80s future, the streets have gangs, feral ghouls, they do in fact have paracritters, etc.