Revised Pickpocketing (3.5e Variant Rule)

Revised Pick-Pocketing
Stealing an attended but not-wielded object from a person, like their coin pouch, is not actually a function of Sleight of Hand Legerdemain. Anyone can do it, since it’s really just grabbing an item from a target. Rules for this special disarm attempt exist in the SRD, but are written from the perspective of attempting the grab while in a fight. Since you probably aren’t in a fight for most of your thefts (and why would you want to be?), we need to make a couple of adjustments.

If you are not involved in a fight with a target and they are not actively keeping you at a distance, you can attempt to take an item that they are not wielding from them. This type of disarm attempt is called a pickpocket attempt, and does not provoke an attack of opportunity when you attempt it. You do not make opposed rolls against the target for the item. Instead, you make a touch attack against your target, who is likely considered flatfooted. The item adds a size bonus to this AC, however, as you're aiming for a rather small target. In most cases, you can just call this size bonus a +4 and not worry about it (which sets the touch AC to 14 if you really don't want to worry about it). You do still get the +4 bonus to the roll if the object is poorly secured or easy to cut free. If you succeed on the disarm attempt, you have successfully cut the object free from its previous possessor, and taken it into your hand (or dropped it if you prefer).

You may only use your unarmed hands, a small knife, or a similar sized blade to assist you, as other blades are too large to be effectively hidden. You can still disarm items from a person with other weapons, but their more obvious nature means you probably start a fight by doing so and should be using the regular grabbing an item rules.

The success or failure of the disarm attempt doesn’t impact whether the target notices the attempt, however, and it’s very possible for them to catch you in the act. To avoid this unpleasant circumstance, you may make a Sleight of Hand Legerdemain check, opposed by their Spot  Perception check, to hide your attempt. If your attempt is successfully hidden, the target remains unaware of the attempt. This would allow you to rob them further if you wanted. If your attempt to hide the pickpocketing fails, your attempt provokes an attack of opportunity from the target. This means that they're trying to keep you at a distance, and you will be unable to pickpocket them further. The regular disarm and combat rules pick up here nicely.

Rule Analysis
So why make pickpocketing more complicated? Well, this setup opens the ability to grab an item from someone in a crowd up to anyone and everyone. If you just want to take an item off of a person and don't care if they catch you, you can do that without resorting to the even more complicated disarm rules. Basing the pickpocketing on a flatfooted touch attack makes higher level characters, who are likely to have always deflection bonuses on them, harder to rob. It also makes characters with uncanny dodge less likely to be robbed since they aren't flatfooted for the attempt, which is good for the rogues of the world and fits genre conventions nicely.