I'm thinking of a few things here in no particular order.
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Difficulty levels improve or lower your score
Score is the universal rating for how well you did in a game, playing the game at 1/10 of the normal difficulty should only be worth one tenth of the experience. Likewise someone playing the game at double difficulty should get more rewards.
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Different challenges/plot arcs for different difficulty settings
You're not going to seriously consider letting people do dangerous things like infiltrating a foreign embassy when they signed a deal with god to give the guards all the brains of half a dead starfish? Add some difficulty specific missions/plot content to add a bit of flavour.
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Is it not nifty? Difficulty slider bar in colour!
Think about it, at the begining of a new game the player will choose his difficulty setting right? Lets use a scale of one to ten with five being the "normal" yardstick.
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(It looks bigger in the ASCII version)
Basically you have a coloured slider bar starting at green on the left (for cakewalk) and red on the right (for masochistic) and have a blue # act as the slider. It gives a visual representation of your difficulty and plus it looks neat.
This would also be easy to do with the SDL version.
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Difficulty settings, random events and you.
I'd like to bring to the table the idea of random events. At the moment the only random events you have are:
You find a $25,000 chunk of ore. Or bandits.
You find the martian princess.
You find a corporate truck that gives jack-all benifits.
What I'd like to see are more random events in GH2, anything from a meteor shower (think Pitch Black (the movie)) to unexpected total faliure of a non-boss enemy Mecha.
On the easiest difficulty setting events will still appear at the same rate as any other difficulty setting, on super-easy they are overall 99% positive (the one percent is: "You break a nail.") but they are also very minor.
On super-hard however, events are far more severe but carry far greater rewards.
I would *LOVE* to see this system in.