I seem to be in a debate with one of my modpack team, and it seems to me that there might be a disconnect between casual and hardcore players what the appropriate level of difficulty is required. I want to please everyone (yeah, I know, but I'd like to try, anyways), and it occurred to me that it might help if there are different formulae for the various Minecraft difficulty levels.

I don't know how doable that is, but I figured I'd ask.

I'm the one he's in a debate with. Thought it wouldn't hurt if I was dropping by as well.
While probably unnecessary, I'm just gonna point you to HungerOverhauls config, which already has an option to scale hunger by difficulty.

And, if this might help, I've actually considered the different calculations for the different levels, and here's what I've come up with.

Hard/Hardcore: The current calculation would make a good home for this setting.
Normal: Let's not diminish returns all the way to zero; but just 1 hunger.

MAX(1/MIN(8, food_hunger_value), MAX(0, (1 - count/12))^MIN(8, food_hunger_value))

Easy/Peaceful: Like normal, except when your hunger is less than a quarter of the bar, a "Hunger is the best spice" bonus applies.

MAX(1/MIN(8, food_hunger_value), MAX(0, (1 - count/12))^MIN(8, food_hunger_value))+(MAX(0, 0.25-(cur_hunger/20)))

I'd have no problem with adding support for this as an option. Would probably have it turned off by default, though.

Works for me; having the option is much better than not having the option. ;)