I think it'd be okay for the EXP gain to not increase for encounters in main. Monsters would get stronger, but players would still have the same level progression so players wouldn't get overly powerful because we messed up the EXP rewards.
Possibly certain fights would be still be easy or would become really hard with leveled up enemies, but I think it'd be more interesting in general than walloping enemies even a single level below you almost for certain. I'm not sure if this script would level enemies down, and I'm not sure whether it should or not. It'd be cool if it would do it to a degree (maybe down to -3 or -4 levels) so the player has a bit more freedom on how he progresses, but not so much that the player could fight the last boss at level 4 or something.
Also I'm not sure how this would affect loot, whether enemies would drop items appropriate to their new level or their default one. I don't think it would be too bad either way. Obviously throwing a blanket script on enemies is going to create some balance problems, but I don't know whether it would actually break anything.
