The Celestial Guard are only a slight upgrade to the Zhanshi with WIP-14 and BTS-3. But lets face it - these guys are still light infantry and still have a miserable BS-11 making their shooting pretty weak. Celestial Guard basically make better Hackers and Lieutenants than Zhanshi.
But lets face it - that's not why you take Celestial Guard.
The best thing about Celestial Guard is the option for the Kuang Shi Control Device and Light Smoke Grenade Launcher - both on the same trooper for a bargain 13 points and SWC-0.5. - The Kuang Shi Control Device is unique to Yu Jing and allow the inclusion of the Kuang Shi troopers. - The Light Smoke Grenade Launcher is the only access to Smoke ammunition the Yu Jing have outside of the Smoke Grenades the Shaolin Warrior Monks carry.
With the poor BS skill you'll want to make sure to keep your smoke shots within the 16" range or you might just end up wasting a bunch of orders.
The Celestial Guard PH-10 is a liability in dodge attempts. Their ARM-1 isn't going to be much help either so be sure to calculate your opponent's to hit values before you decide to dodge. It might just be worth that one risky shot with a Combi Rifle to maim an attacker.
The combination of the smoke ammunition that the Light Grenade Launcher has can be exceptionally effective when combined with a Hsien trooper using the Multi Spectral Visor L2 (MSV2). The Hsien shoots through the smoke at BS-14 with no disadvantage while his opponent shoots back with a -6 mod - or worse.
Most any smoke generating trooper is a high value target and is best brought down early in the game. The ability to create a Zero Visibility Zone at will and wherever needed is a major game control that cannot go unaddressed. Simply put - prioritize this trooper early on.
If a Celestial Guard Lieutenant is desired then its cost is only 2 points more than a Zhanshi - is the 1 better WIP-14 worth it?
The Light Smoke Grenade Launcher is an almost 'must have' in Yu Jing - especially in combination with a trooper with Multi Spectral Visor L2 (MSV2) (e.g. Hsien, Bao Troops, Yaoxie Rui Shi). That combination provides a very effective kill combination that is hard to beat.
If you want to go the cheap Kuang Shi route then the same Celestial Guard is a must have. You can rack up 4 regular orders and 4 impetuous orders for a mere 20 points.
Keeping the smoke generator hidden properly is a key to keeping her alive. If you don't have the first turn then you'll need to have her keep her head down. But don't leave her alone as she tends to be a target for infiltrating enemy and impersonating assassins. If you have the first turn then simply make sure she is positioned to place her smoke in the most effective location starting on the first turn.
Active Turn Role
Smoke generation should come early in your active turn. Get your troops moving from behind a Zero Visibility Zone early and often. Her BS-11 is a liability so be sure you are shooting smoke under 16" to give you the +3 you need to land it.
In ARO a Celestial Guard can be an effective shooter - especially if you have multiple troops firing on the enemy. It forces the enemy to split their fire or face a possible hit from a cheap troop. In effect - if you can shoot from cover - why wouldn't you? The Celestial Guard can't dodge very well with the PH-10 so if the enemy is in the open, in the Combi Rifle's favored range (less than 16") it would be a waste not to take the shot. Just remember that the smoke generator is more valuable on offense than the Combi Rifle she carries.