I don't know, since I've never actually been pickpocketed, but I'm thinking that, if I reach for my wallet, and it's not there, I'm going to notice.
Fast travel can cheese it, but this always works and feels more realistic. It's basically the same mechanism as in Larian's previous DOS2 game, although that had a one-time pickpocket restriction per merchant. and per party member. They should bring that back.
That would be just a band-aid solution to a mechanism which is more an exploit than a feature in Larian games. I feel Larian should do more to balance pickpocketing becoming the easiest way to get rich/powerful fast. Once you understand how the system works, you are pretty much guaranteed success. Besides, success is just a single save scum away.
I'm hoping for more roleplaying moral dilemmas where you can obtain ill-gotten goods, rather than a simple gameplay mechanic. I'm hoping for a hidden reputation system a bit like in the original games. If things start being stolen/disappearing when the party arrives in an area - all of them will be under suspicion even if there is no direct proof. Social skill checks should be made more difficult. Stolen items, depending on rarity, should always have a chance to be recognized when equipped on a companion. I want the possibility a friggin' Flaming Fist squad spawning yelling "I AM THE LAW!" as it proceeds to arrest or attack you or a "crime hunter" squad who investigate larger thefts and where possibly innocents are falsely accused/arrested. Anything but a quick and easy way to be more rich and more powerful as Larian usually opts for.
So what in any of this prevents "save scumming"? Assuming you're not caught, how does that Flaming Fist squad know it's you? My GF at the time and I did a murderhobo run of BG. We killed everyone and everything we saw. At the end of that playthrough, we had to abandon it, because there were squads of Flaming Fist everywhere, and even rest ambushes were Flaming Fist. We were completely unable to progress the game. It was fun, in a way, but we didn't get very far before we had to quit, because after a while, it became unfun. The system you're laying out here is no less "exploitive" than what's in game right now, with people automatically assuming it's the PC's group that's responsible. At least in the current system, there's still a chance that you can be caught, either by a failing roll, or some random passerby taking you out of stealth. That's worlds better than being locked out of content because NPCs won't interact with you because of your reputation. I mean, even in BG, I always wondered how, with no witnesses, the Flaming Fist always knew it was us, and where we were...