I recently finished reading Tom Clancy's book Marine
and in it he mentioned that the USMC uses a variant of the LAV
that is armed with stinger missiles and a GAU cannon. Apparently
the USMC is very happy with this vehicle and is planning to order more. Being a medic and not a AD gunner, my question to the gunners out there is:
1) Is this system an effective and reliable weapon?
2)Would it be more cost effective?
3) Could it play an important role in air defence in Canada?

I spent awhile tonight on the internet looking for a picture of said wpn system, however, I was unable to find one. I've only experience with the US Army Avenger system. I'm not an AD Gunner (Mr Magoo may be lurking around ... whereever bird gunners hang their hat when they are not being used), however, in answer to your questions:

1) Is this system an effective and reliable weapon?

I'll have to go with the information you brought from Tom Clancy (who am I to argue with Tom Clancy?). However, in a perfect world, the Marine Corps LAV variant would fit in quite nicely with our movement to medium weight, all wheeled fleet of LAV.

But, there is nothing wrong with the AD Eqpt (ADATS, Gun/Skyguard, and Javelin) that we have. The trouble is we don't use it for what it is designed for and it's only become an expensive air force training tool. The Army has not been kind to the Air Defence.

2)Would it be more cost effective?

Probably not as we spent a billion dollars on eqpt we don't use properly. What's to say we would spend more money (that we don't have) and purchase new eqpt (simply because it is wheeled) and don't use it properly either.

3) Could it play an important role in air defence in Canada?

Same answer as question 2.

The Stinger system is a "fire and forget" missile, the Javelin
on the other hand is not. An operator can cause the Javelin
missile once fired to leave its track, go ballistic (straight up)
and self-detonate harmlessly away from the once-intended target.
This is of course an important safety feature because for both systems the IFF (identify friend or foe) is entirely left up to the "Mark 1 eyeball" of the operator. In this day and age of coalitions, we can face the Iraqi Air Force with their MIGs, and have the Syrians on our side with their MIGs.

The Stinger's other failing is that it is a heat-seeker, so it's
best to fire it at the back of an en aircraft. In a lot of cases
in the fashion that Canada deploys AD manpads systems that means
the aircraft will already have dropped it's payload of munitions
on or about the intended target.

Having said that the Americans have a different system of employing AD. They saturate an area, believe heavily in interdiction missions and in ambushes with the Stinger. They pick potential fly routes and cover them, when the en flys by everybody can open up. Canadians for largely economic and philosophical reasons allot areas of responsibility
and track targets passing off the option to fire from one detachment to another as the aircraft enters a det's area of responsibility and then exits.

The trouble with purchasing that variant was it would give everyone "gun" envy!

With the ADATs (AD Anti-Tank system) the turret is so heavy
that the veh can be unstable and has difficulty moving along,
it's very tough on the power-pack.

Originally the plan was that the Leopard would be replaced,
and the 120 Leopards would be divided into two groups, 60
would be kept as is for Armr Recce, and the other 60 would be
ADATS and Engr vehs. How sweet that would have been!