These are basically a few ideas on how to alter the functionality of the Promethean Weapons to differentiate them from the rest of the sandbox. Aesthetically, they’re amazing, functionally, they’re a bit average.
Incineration Cannon: Combine it with a few of the Reach Plasma Launcher’s abilities. Keep the single-shot, but make it so that the blast damage/number of splash projectiles can be increased by holding the trigger down, characterised by a reticule change. This means it’s no longer a one-shot kill-all weapon, but something that has to be charged and used strategically.
Light Rifle: Keep the dual-firing mode functionality, but make it so that instead of the current mode, unscoped fires a large projectile with slow firing speed, while scoped fires a shield-stripping sentinel-esque beam that eats through ammo like a devil.
Binary Rifle: Works for me already. The laser sight balances it nicely.
Boltshot: (Not my idea) Change the charge shot from a shotgun blast into a single projectile that passes through shields, doing negligible health damage but with the potential for a straight headshot. Perhaps decrease accuracy to compensate.
Scattershot: Add in a charge feature for a burst-fire mode, perhaps increase range and nerf damage slightly. Also, increase damage whilst bouncing off walls for awesome trick-shot montages.
Suppresser: Add ability to convert half a magazine into a highly-visible hardlight blade for use in melee combat. Disintegrates and causes overheat on use.