Love them or hate them SPG's are in the game, and they have always been a contentious issue within the community. Always sparking, arguments, private in game messages after battle, both toxic and complimentary. The mechanics have changes over the patches, in the past the AP shells and one shots to the more recent stun mechanic. All from a vehicle class that cannot be seen, unless physically spotted, and at a far greater distance away than the render range of tanks that can shoot you whilst they are unspotted.
You could say that it is unfair, but this is possibly 'balanced' out with no armour, very little speed and long loading times. I am an SPG player (and I also served in the Royal Artillery in the British Army a number of years ago), but I do agree that something could be done about this class of vehicle.
I have thought of something, which of course are open to debate about how the SPG 'fairness' could be altered. Currently in the HUD there are a number of direction of fire indicators (should you chose to use them) highlighting a direction of fire.
For me this is perfectly acceptable, as it informs you where you have taken a hit from ,even if the enemy are not spotted BUT they are in render range of your vehicle. It does also tell you when an SPG hits you, however they have probably hit you from the far side of the map. Now, you could justify the argument saying this is not fair, due to the distance away they are etc, or counter that with the above characteristics of an SPG, armour/reload/mobility etc.
As 6th sense is a skill in the game, you know when you have been spotted, so why not make this a skill ? Not just a built in function of the mini map?
One proposal I have would be a mini map indication-For the players that have been hit, with the crew member trained in the skill.
A box like the one above would flash on YOUR mini map when you were hit by an SPG, of a rough indication of a number of grid squares, in the reason of fairness, I chose 6, 9 could also be an option but any less would in my opinion be unfair.
This would give you the ability to highlight the rough area to your allies, the location of an SPG-all which happens in the game anyway with the current Fire Direction Indicator so it would be nothing new.
Also included in the 'SPG Informer' skill, the addition of the area an enemy SPG is targeting ON YOUR SCREEN ONLY but only for say a maximum of 3 seconds, currently like the one in game for your own team with the yellow circles, but in this instance it would be red , so you know yo would have to relocate