let's see what pain mode usually does in games:

• crows explode

• more enemies

• probably some secrets

• maybe a new ending too

for the first one, I feel like it doesn't affect most games since they're mostly linear, and some games mitigate the limited saves by giving you ones that you can use anytime, ie. baby crows. I honestly do not feel any difference between infinite saves and finite ones, unless there's a section that can be cheesed by save scumming, such as recruiting buckets in painful.

as for the second one...ehh I mean I guess it does make the game more "painful" by giving you more fights, but I feel like your experience wouldn't be that much different whether you fight one new enemy or not.

secrets and ending seems fair enough, as it rewards the player for choosing the supposedly harder difficulty with things unique to it, this is probably the ones I have little to no issue with, though again, you probably choose pain mode by automatically assuming that there are stuff that doesn't exist in normal mode. so why not just make an inherently challenging game with all the fights, secrets and endings?

just another food for thought. let me know what you think.