I take a blend of M119 and 120mm mortars for the Reserve Artillery. Add a LAV based 120mm Mortar as a Interim SPG. I buy the mortars outright. The M119, likley we could convince the US to lease us 50 or so to supplement the C3. This is all doable in our current and anticipated budgets for the near future.
Lets crunch some numbers.
I've just counted up the number of gunners in the Res F artillery from the 2020 Gunners of Canada. There is a total of 2,124 (give or take a counting error or two) including bands in sixteen regiments and three independent batteries. Regiments vary in strength from a low of 55 to a high of 184. Independent batteries from 27 to 82. An average of 122 per regiment and 54 for the independent batteries.
So what do we do with those gunners? Well I'd say you can probably discount the numbers by 15% for bandsmen and those unfit for service (and I think I'm undercounting those) which leaves roughly 1,800.
What do we need to fill out the regular force regiments? Each regiment has 2 batteries of 4 guns each when it should have three of six guns. At roughly 35 pers for each of the six two-gun troops needed (210) and 130 pers for each of the three missing six-gun batteries (390) we need 600 reservists just to round out the three Reg F regiments - plus 30 guns and all the associated gear (lets not complicate things by wondering where the trained weapon and radio and veh mechs come from)
So that leaves 1,200. What else do we need for an army the size of Canada's? - air defence - we need air defence. That's around another 5 - 600 folks. Many of these need to come from the Reg F but every one which comes from one of the three Reg F regiments needs to be replaced by a reservist in whatever job he held somewhere else. So let's say 600 for air defence.
That leaves 600. So what else should we need? - a general support regiment? a precision rocket regiment? a few weaponized UAV batteries? more STA?
So where am I going with this rambling?
Simple - there is no room for light guns or mortars or whatever you might consider.
To properly plump out the Reg F regiments will take 30 guns and a third of the reserve force - all of these should be trained on whatever weapon system the Reg F units own. Specific Res Regts need to be trained and designated to fill those roles and be equipped to fill the equipment shortfalls that currently exist. (and yes IMHO we need an SP, either tracked or more probably wheeled for two of the brigades - which means buy appx 40 new guns and concentrate the M777 in a light brigade)
Adding an air defence role to the artillery should require a full regiment (it probably won't be because we'll probably want to make do with a battery - but it used to be a regiment and, IMHO, needs to be to properly support a three brigade army) That will eat up the second third of the reserves - many of whom will become air defence specialist and the remainder, those replacing the Reg F air defenders will, like the first third, need to specialize on whatever equipment their Reg F unit holds.
The issue is the same for the last third. They need to specialize on, be equipped with and be organized to form those general support or STA or rocket or UAV systems that are required.
Take good notice of something here. There simply aren't enough Res F gunners in the system, as it is, to fully man the weapon systems that we have and the few additional ones that that we need which are critical capability deficiencies. We do not have enough to make mortar platoons for infantry battalions or light gun batteries to support light brigades (other than whatever the Reg F might field). The Reg F artillery is critically understrength. We can hope that more modern weapon systems will be able to require less crews but I wouldn't count on it. An automated SP with a three gun crew needs a good ammo det in support to keep the beast fed.
We can continue to function with the system we have where our deployments commit no more than two gun batteries per year in six month rotations. Remember though that every one of those years ate up a large part of two entire regiments augmented by a whack of a lot of volunteer reservists all of whom went through lengthy predeployment training cycles that allowed the reservists to integrate. If, however, we are faced by a situation where we need to commit more than that and keep it sustained, or are required to deploy rapidly then our current system is sadly lacking. It makes me think of the homeowner who for years has not paid any premiums on fire insurance because - well so far - there's been no fire. With every year he gets by without a fire he becomes more and more convinced he doesn't need the policy. Canada's artillery (and its armoured corps) is a lot like that.