[@Deadnaut]  This does open the possibility for us to launch your character while his armor is light, then make your armor weigh more mid air and crash into the ground with a mighty explosion.  We could make your character into a projectile.  This is of course if upon transferring weight it conserves velocity, not total applied force.

The other possibility is that if the armor acts on total applied force rather than on previous velocity, your character can take a step while the armor is heavy and once sprinting make the armor lighter, turning the mass into velocity and literally flying into your opponents at mach 3.  Your guy should be flying, not walking.

I think that your armor is the most powerful weapon any of us have.

I'm looking too much into this, aren't I?

EDIT: I did the math and realized your character would have to raise mass to a ridiculous amount in scenario 2 in order for it to be an effective method.  Blast.

EDIT 2: We could instead launch you OVER the enemy in scenario 2, increasing your mass so much that your velocity drops to zero, and letting gravity turn your new heavier mass into an asteroid capable of wiping out all life on the planet.  Back to overpowered again.

EDIT 3: Why am I doing math of my own free will at 1:15 in the morning?