So, I was wondering, would it be possible to eliminate the player's effect on NPCs' leveled items?

Normally, when an NPC's leveled items are determined, the game uses whichever level is lower -- the NPC's or the player's. So a level 5 NPC is limited to the level 1 results from their leveled list items if the player is level 1.

I don't think this can be accomplished by editing leveled lists, because I still want weaker NPCs to be limited to weaker items like in vanilla.