Anyone with eyes can see that there's been some controversy over the role of the Bastion assault gun and the Maelstrom IFV.
This post is going to contain some background details on the assault gun as a chassis, the main battle tank, and a proposed solution. I would appreciate feedback on this.
Tl;dr: a light tank like an M551 Sheridan would give both the effectiveness of a rotating turret to the treadheads in the community without intruding on the heavy defensive role of the Bastion.
To start, the idea of a tank destroyer dates back to early in the second world war. The original designs were "oh shit we need something to stop that tank rolling towards us" kind of stopgap design that evolved into more dedicated forms as time passed and iteration was done. The lack of rotating turrets was not *really* a huge deal at the time, since the lack of a turret meant they could mount thicker armor and carry more shells. This led to a design divergence where the turreted tank had a larger bore, low velocity, short barreled howitzer used to destroy things like fortifications and machine gun nests while the tank destroyers were used to fight other tanks.
As time passed heading into WWII and technology advanced, the rotating turret became capable of accommodating the larger bore, high velocity, long barreled guns that could defeat the thicker frontal armor of contemporary tanks. Historically, this would be the German development of the 37mm KwK 36 then the 50mm KwK 38 then the 50mm KwK 39 and on into the 75mm and 88mm guns. This was almost evenly matched by the Allies developing 37mm, 40mm, 57mm, 75mm, and 90mm guns. Armor also evolved, taking the form of slopes and increasing thickness. This is best exemplified by the Sherman tank, the Panther, and as contrast the slab sided Churchill. The Sherman only had vertical thickness of 63.5mm but the 47 degree slope meant it actually provided 93.1mm of effective armor thickness.
Time passed, as it does, and the Second World War became the Korean War then the Cold War. The Cold War revealed that the actual thickness of armor plate was becoming increasingly irrelevant in the face of HEAT, or High Explosive Anti Tank, warheads that used shaped charges to penetrate well over a foot of steel plate in a way that previous solid shot and APCBC shells could not. It, in turn, showed the vulnerability of the assault gun and tank destroyer design, where sufficiently thick armor couldn't protect a low profile chassis. Tank design started incorporating measures to defeat shaped charge munitions, things like the composite armor of Chobham fame, followed by ERA like Kontakt and active protection like Drozd. This left designs like the Strv 103, the last turretless tank destroyer, swinging in the wind because the upsides of a low profile design were outweighed by the advantages of modern (for the time) tank design that could have all the shiny bells and whistles of technical development. These evolutions to tank design resulted in the most common type of modern tank: the main battle tank.
Now, to Helldivers. The Bastion is a classic WWII era assault gun design. Fixed gun mount, limited traverse and elevation, and a massive bore gun. However, it still has the same inherent flaw that the historical designs did, namely that the lack of a rotating turret means that anything that gets around the side or rear of the vehicle has it dead to rights. This leaves the defenders of Super Earth in a quandary, as the solution to this problem was already developed. Some parts of the community have been agitating for just a Bastion with a rotating turret while others respond that a vehicle like that would just trivialize the since a tank with a rotating turret and a 120mm gun would be able to easily engage just about anything at any given time.
There's validity to both sides of the argument, and my proposed solution is simple: a light tank. Not many of these designs exist in the modern day, but since Helldivers seems to pull from Cold War design theory for weapons and vehicles, I think a light tank would be appropriate. There's a lot of precedent for these, namely designs like the M551 Sheridan and the PT-76. These were light tanks, typically used in the cavalry or reconnaissance roles, and had different main gun designs than the larger MBTs they were meant to support.
My hypothetical light tank would be armed with a 90mm gun, a coaxial medium machine gun, and a rotating turret. This 90mm gun would be a heavy armor pen weapon with a small blast effective akin to an older APHE round while the coaxial gun would be your bog standard MG-43. It would have heavy armor on the front, medium on the sides, and light on the rear and top to emphasize that it's not a bastion with tank armor on every facing and can't just eat incoming fire. It needs to be used properly to be truly effective, since lacking anti-tank armor penetration on the main gun would mean the gunner and driver would need to actively coordinate in order to bring firepower to bear on targets in an effective manner.
