It has already been stated that Savoy will be included at a later date, currently it's not in because there was initially a lack of sufficient info for its lords, and the un-merging of savoy and the Austrian Habsburgs/HRE will take some time as it also requires more Austrian units to be created to take the place of the Savoy units currently on the Habsburg/HRE roster.
As far as suggestions go, I don't really like the implementation of guns in their current state - slow, cumbersome pieces that are very hit or miss in the dealing of massive damage.
Period artillery was an attrition weapon (baring the odd bit of short-range fire, which didn't happen anywhere as frequently as it did later in the 18th century) that wore down the enemy with a continuous barrage - frequently starting with an artillery duel, and then moving on to target horse and foot as those moved to engage.
In addition to that historical aspect, in gameplay terms guns are a large element of randomness on the battlefield - you can win or lose a fight with the first long-range salvo, and then you can have a battle where both batteries fire for the duration with very little noticeable effect. It's tolerable in a SP game, but it's still bad gameplay/design as far as I'm concerned.
As such, I'd propose a significant increase in the ROF of the guns, more so for the smaller pieces (a 3lber should match small arms ROF), maybe with a gradual slowing of the ROF over time, and a significant decrease of the area of effect,
If the scripting allows, I'd also scale the area of effect and dispersion of the impact with range to target, so that lethality increases as the targets get closer.
Since the scripting allows for casualty-free shooting through own troops, short-range fire shouldn't be too effective, to simulate the fact that the guns are being masked by their own troops.
So far, artillery has spawned forward of the other troops in most (all?) my battles, but immediately began firing at the troops - ideally, the target selection process could be altered to where the fire can only switch to troops once they are closer to the guns than enemy pieces, to simulate artillery duels.
I know it's still early for this kind of detailed battle balancing work, but since the guns probably can't be adjusted and changed as easily as weapon or troop stats to get the desired results, I thought mentioning it early would be beneficial.