Game-Modes and governmental interaction.

[Whirligig Girl]

Beginner

Ship parts cost 75% as much.

Little reputation loss for dead Kerbals

Larger window for part-test conditions.

More science gained for Mun, Minmus, and Duna.

Large monthly governmental funds with positive rep, no budget cuts.

Easy

Ship costs 90% as much

slightly larger window for part-test conditions

Large Monthly funds with positive rep, small budget cuts with negative rep.

Normal

Budget cuts and Funds proportional to each other.

Hard

Ship costs 110%.

Slightly smaller part-test conditions window.

small funding with positive rep.

Random budget cuts with rep lower than 45% of maximum positive.

No re-spawning kerbals

Manley

Ship costs 130%.

slightly smaller part-test conditions window.

no re-spawning kerbals

no quickload/quicksave

no revert flight

random budget cuts with rep lower than 85% of maximum positive.

Impossible

Ship costs 200%

very specific part-test window.

no cheat menu

no re-spawning kerbals

no quickload/quicksave

no revert flight

random budget cuts with rep lower than 99% of maximum positive.

no government funding

[Artophwar]

Values can always be adjusted but this is the kind of difficulty scaling I would like in game. I would probably add lowered science from missions and or complete removal of science gain from missions at higher difficulties so you have to use the science parts to progress.