Would be cool if each class would have a variant (inside the same class not a new class) with different skills and weapon rules, examples:


Heavy:

Something like primaris aggresors with only seconday weapon and melee, the skill could be missiles, if you press the skill it would launch 1 missile to the enemies in priority order (terminus > extremis > majoris > minoris), and if you hold it would be something like red dead redemptions dead eye where you can chosse how many missiles go to wathever enemy, they look like this --> https://www.warhammer.com/en-GB/shop/Space-Marines-Primaris-Aggressors-2020?queryID=69c15923c13ecced7d95f9bbfc97f62f


Bulwark:

Something like emperors champion from black templar where you change the role of the class from support/tank to be a full on damage dealer, weapon rule would be the same melee and seconday weapon but you would have no shield and the melee weapons would all be available, skill could be the titus ability from the campaign , something like this --> https://www.warhammer.com/en-GB/shop/black-templars-emperors-champion-2021?queryID=7f0edf4cb7e4f5351a1ca8f0b9b71205


Sniper:

weapon rules would be melee an secondary weapon, no primary weapon beacause the skill would be a heavy sniper rifle, they would look something like the primaris eliminator with helmet connected with the scope of the weapon --> https://www.warhammer.com/en-GB/shop/Space-Marines-Primaris-Eliminators-2020


These are a few examples I came up with but I am sure there are many posibilities, let me know what you think.