In the style of Metal Gear Solid 2's difficulty modes, which change most aspects of the game. Let's consider base DS1 to be "normal" mode; in easy mode, I propose:
- Universal HP damage reduction by some percentage (let's say half), but not to Stamina penalties and not to instakills
- Ailments are harder to apply to the player and easier to remove
- Enemies stagger easier
- Humanity is more common
- Some areas have rearranged enemy placements with different or less enemies (the pit at the bottom of the Catacombs isn't actual hell anymore, and neither is the 3-gargoyle area in Anor Londo when you keep getting fired at by the archers)
- The weight threshold for rolling is raised so that light rolling is easier
- Some bosses have different attack patterns and simply do not use some attacks (I'm not sure on the specifics)
- The player can teleport from either Blighttown bonfire to Firelink Shrine and vice versa once they've been activated (before you get the Lordvessel), so that players whose weapons break don't have to climb out again; same for Ashen Lake, so the player doesn't have to climb back out of the Great Hollow before getting the Lordvessel
- More bonfires
- The lantern shows more in the Tomb of the Giants
- Curse does not exist (Basilisks instead inflict Toxin)
- The Toxin dudes in Blighttown no longer exist
- Bed of Chaos does half knockback and half stamina damage on shield
- Give the player 2 extra ring slots?
Not too sure how one could fairly make a hard mode, but the inverse of these would be a good start.