How about RUN... Which adds 10-40% (more skill points) speed for however long you want (sustain) but takes stamina increasing per turn. So activating it for 5 turns could cost +-25 stamina (3,4,5,6,7 = 25) stamina for 5 turns, but 33 for 6. And so on. Stamina usage could go up as speed gain goes up? Not sure if it should.
Speed advantage is reduced by 50% (30%*50% = 15% speed increase) with heavy armor, and reduced by 66% for massive armor...
Meaning, you don't go much quicker with armor, but you pay a lot more (cause you are fatigued already), meaning again, it's really more for rogues and other classes who doesn't use heavy armor / massive armor.