I think I might have made a comment about custom firearms but I am not sure, however I would like to have more game modes than just story, or an augmentation of the story.
One Gun Run: The title says it all; a mode where you only have one gun that receives several buffs to compensate for just only having one firearm with each “family” of firearms getting a special buff and depending on the quality of the firearm in question it will either receive a decent buff or none at all.
No other weapons drop in the mode but grenade mods, COMS, ammunition, shields, and other non-firearm related drops will still spawn.
Iron Man: No checkpoints, no respawns, no kitty wheels. You die, you are done. To ensure you do not die too awful much Claptrap will yammer away for close to a minute every time you die about how disappointed he is you failed as a minion to serve your master.
Broken Skull: No shields, no pity, and no returns. Players receive a 50% health increase to compensate and healing hypos drop with much greater frequency. Melee oriented enemies spawn much more frequently as well.
KABOOM!: All weapon totting enemies always spawn with explosive weaponry and toss grenades far more often. Suicide psychos spawn in droves, explosive barrels are a dime a dozen, and rocket launcher totting enemies are common. Grenades and rockets drop with more frequency so it is not an exactly one sided affair.
Badass Bonanza: Here a badass, there a badass, everywhere there be a badass! All non-boss or unique enemies always spawn as badass enemies. Loot quality is substantially higher in this game mode to compensate for the tears that will be shed.
Medieval Mayhem: No guns, no grenades, no shields, and no mercy. Just good ol’ fashion fisticuffs. Players receive a 150% melee damage bonus, 20% speed bonus, and 50% damage reduction bonus. Dealing melee damage heals the player for 15% of the damage dealt. Action skills recharge 20% faster as well.
Glass Jaw: Hit harder, but have the physical constitution of a piece of paper about to be struck by a recently sharpened machete. Players deal 100% more damage but lose 50% health and shielding. Player knockback is more severe being at a 150% increase so you may want to reconsider getting into a slap fight with the God-liath over yonder; he may very well send your corpse into orbit.
Those are off the top of my head but the idea is that Borderlands 3 have quite a few ways of changing up the difficulty that would suit everyone’s tastes.