Yes it would be nice to be able to run at diferent speeds.
Maybe it could be something like this:
Walk: Slowest, fatigue doesn\'t decrease at all.
Jog: kinda fast, fatigue decreases slowly.
Run: Fast, fatigues decreases same rate as it does right now
Sprint: Very Fast, fatigue decreases quickly
if more are needed then they could be added somewhere in there.
Then monster speeds should definitely be changed. Something that can fly should be pretty fast. Bigger, fatter, heavier things should go more of a jog pace.