Just throwing this in:
Armour limited movement because of its weight, but that weight was most prominent in wearing you down faster. A full suit of medieval plate armour with weaponry included weighs just as much as a modern soldier's battle outfit including weapons. Only difference: plate armour is well-distributed over the body, while a modern soldier has most of that in his ballistics vest and backpack.
And a modern soldier can still jump, run and do everything.
While I can already hear you saying that it doesn't restrict as much as plate armour, you are probably right, but one has to understand that plate armour was designed for fighting, and most if not every move one WOULD make during a fight is possible as a result of that.
So if we are going the realistic way, plate armour would be utterly OP: Despite the weight it'd give less speed penalties than heavy chainmail armour, while protecting from most if not all ranged weapons further than point blank, while being nigh invulnerable from non-heavy hits.
Gameplay-wise you'd have to find a balance in this, but I'm just throwing my realism cent in this realism board here.
