Handling a Snatch-and-Grab

[Serpentine]

I'm gonna have something valuable of a character's snatched in a very organised theft, complete with casing, scoping, watch and back-up. I'm slightly uncertain about the best way to handle the mechanics, though, and would like some input.

The RAW (of the SRD) says this:

Disarm
As a melee attack, you may attempt to disarm your opponent. If you do so with a weapon, you knock the opponent’s weapon out of his hands and to the ground. If you attempt the disarm while unarmed, you end up with the weapon in your hand.
If you’re attempting to disarm a melee weapon, follow the steps outlined here. If the item you are attempting to disarm isn’t a melee weapon the defender may still oppose you with an attack roll, but takes a penalty and can’t attempt to disarm you in return if your attempt fails.
Step 1
Attack of Opportunity. You provoke an attack of opportunity from the target you are trying to disarm. (If you have the Improved Disarm feat, you don’t incur an attack of opportunity for making a disarm attempt.) If the defender’s attack of opportunity deals any damage, your disarm attempt fails.
Step 2
Opposed Rolls. You and the defender make opposed attack rolls with your respective weapons. The wielder of a two-handed weapon on a disarm attempt gets a +4 bonus on this roll, and the wielder of a light weapon takes a -4 penalty. (An unarmed strike is considered a light weapon, so you always take a penalty when trying to disarm an opponent by using an unarmed strike.) If the combatants are of different sizes, the larger combatant gets a bonus on the attack roll of +4 per difference in size category. If the targeted item isn’t a melee weapon, the defender takes a -4 penalty on the roll.
Step 3
Consequences. If you beat the defender, the defender is disarmed. If you attempted the disarm action unarmed, you now have the weapon. If you were armed, the defender’s weapon is on the ground in the defender’s square.
If you fail on the disarm attempt, the defender may immediately react and attempt to disarm you with the same sort of opposed melee attack roll. His attempt does not provoke an attack of opportunity from you. If he fails his disarm attempt, you do not subsequently get a free disarm attempt against him.
Grabbing Items
You can use a disarm action to snatch an item worn by the target. If you want to have the item in your hand, the disarm must be made as an unarmed attack.
If the item is poorly secured or otherwise easy to snatch or cut away the attacker gets a +4 bonus. Unlike on a normal disarm attempt, failing the attempt doesn’t allow the defender to attempt to disarm you. This otherwise functions identically to a disarm attempt, as noted above.
You can’t snatch an item that is well secured unless you have pinned the wearer (see Grapple). Even then, the defender gains a +4 bonus on his roll to resist the attempt.
Sleight Of Hand (Dex; Trained Only; Armor Check Penalty)
Check
A DC 10 Sleight of Hand check lets you palm a coin-sized, unattended object. Performing a minor feat of legerdemain, such as making a coin disappear, also has a DC of 10 unless an observer is determined to note where the item went.
When you use this skill under close observation, your skill check is opposed by the observer’s Spot check. The observer’s success doesn’t prevent you from performing the action, just from doing it unnoticed.
...
If you try to take something from another creature, you must make a DC 20 Sleight of Hand check to obtain it. The opponent makes a Spot check to detect the attempt, opposed by the same Sleight of Hand check result you achieved when you tried to grab the item. An opponent who succeeds on this check notices the attempt, regardless of whether you got the item.

I'm thinking something along these lines:

The target gets a Spot and/or Sense Motive check, opposed by the thief's Hide (in a crowd) and/or Bluff check.
If the target succeeds, it goes as per Grabbing Items, above, except (maybe) the thief can use Sleight of Hand instead of an attack.
If the target fails, they are caught by surprise. The thief does a Sleight of Hand check (possibly taking 10, as they can take their time getting the timing and angle etc. right). The target may do a Reflex save, probably with a DC equal to the Sleight of Hand check.
If any attempt to grab the item fails, the thief must do Disarm/Grabbing Item attempts to try again.
Once it's grabbed, it's pursuit rules, like in whatever book or whatever it's written down. I think it was basically, if speeds are the same, they do Dexterity checks. Except the thief will have a partner getting in the way of pursuers.

Does this seem like a reasonable system?

[dsmiles]

Can't see why it wouldn't work. It seems fair.

[Serpentine]

Heh. I guess I'll have to make do with one approval Thanks.