Actually, I've managed a fair level of success building a "one size fits all" PSK and BOB. It does require the inclusion of a few items that are environmentally specific, but otherwise suits me in just about any situation I could find myself. What does adjust more to the environment is my EDC. But even at that, it is more a matter of swapping things in and out of my kits into my pockets or my man-purse.

I would have too much trouble keeping up with "what's-in-where" if I had different PSK's for different environments.

I have my baseline EDC that I stuff my pockets with regardless of where I'm going (airline travel excluded of course).

I live in a medium-sized city (Baton Rouge) and figure the same problems (shelter, water, food, first aid, etc) would be the similar as if I were in the woods if we encountered a 9-11 level problem (no twin towers but plenty of chemical plants)

My "field pouch" (with potable water tabs, space blanket, N-95 respirator, etc) that lives in my EDC backpack gets transfered over to my camelback if I'm going hiking.

I DO have a city kit & a wilderness kit.
Both are based around tobacco tins, the city kit has more in the way of lights, money, credit card/atm card, phone cards, batteries, meds, whistle, FAK, N95 mask, SAK etc & NO fishing kit, wire saw etc.
Obviously, the wilderness kit has all the usual goodies in it to help provide heat, light, food, water, protection, location etc.
The city kit lives in the small zip pouch of my Maxpedition Falcon which now seems to go everywhere with me, usually with a lightweight waterproof & a 1litre Nalgene bottle of water.
I keep a packed bergen as my BOB in the trubk of my car AND a briefcase containing a brew kit, spares of both kits, Frost Mora, 2 Flaslights, FAK, Spare mobile phone, emergency charger for phone, leather man, SAK, mess kit & various other odd n sods.