I want for you for a moment to think about what is SPA in your mind, visualize artillery. Got it? good, now throw all of that out the window, because that is not what's in Hell let loose. The false "SPA"s in game are all horrid but I think emphasizing the worst one will do the whole topic justice, lets talk about the Brummbär.
The real Brummbär and her variants were infantry support guns, designed to provide direct fire support and destruction of fortified positions and buildings.
In HLL the opposite is true, the practical way to use "SPA"s is in a 300-600 meter sweet spot from your target. Any further and typically you will be in limited operational zone, to prevent firing and camping with the gun at ranges the devs have deemed unfair.
keeping these limitations in game would be fine if not for a few details.
The Brummbär is helpless in her current state. The devs have chosen the variant that was not only one of the least produced, but also one that lacks any form of self defense in terms of machine gun fire outside of its main cannon. This would most likely be fine if not for the fact the main gun cannot be fired on the move, and her limited horizontal aiming range compared to her peers. The "sight" and the mils in the scope are also too barebones to use, and calculating for the negative or positive slope you are on is tedious at best. She is too weak to give close support fire, and too map constrained to stand a chance when trouble comes. The experience is "satchel bait simulator".
I suggest modifying the model to the Ausf IV variant to include a machine gun (see pics), and her main guns horizontal range and speed be increased to keep up with her peers. Furthermore all SPA should be given better sighting systems (perhaps the gun automatically adding the slope mils), and the ability to shoot on the move, if the map limitations are to be kept in place. The "SPA"s added were meant for close support IRL, they would fit better into the game that way as well.
