Attack speed:
As it is now the speed of special moves is determined by the difference between the agility of the attacker and defender. My idea is that that the player starts with attack speed of 100% when wearing no armor or light armor. Every piece of equipment decreases that speed by a certain %. For example: every piece of leather armor decreases that speed by 3%. Heavier armor decreases the speed even further. So a guy wearing only light armor would have a normal cooldown on moves while a guy wearing leather armor would have a 12% (4*3% i think) increase in the cooldown of the moves. (numbers are just an example - needs to be balanced ofc)
Armor bonuses:
Because of the speed decrease the armor provides some defense bonuses to the combat. By that i don't mean only deflection and absorption but also weight. Between two options of speed and more def weight it gives the player something to think about weather he is more comfortable with more speed or slower paced combat with more defense. I think this would actually provide players with some combat options. A more armored player can hold few more rounds gaining IP cuz he has more def weight while the faster player needs to be on his toes about his defense.
Armor type restricting moves and maneuvers:
Another aspect of wearing different types of armor is thinking which moves you are gonna use. A guy wearing heavy armor for example cannot use fast moves such as dodge or jump. While the light armored guy cannot use defensive ones such as oak stance. (This needs more thinking

Discuss
There is something i forgot to mention: My idea only works if the idea of Potjeh (i think it was he who said it) that bows do constant piercing DMG so that you can survive a shot with all armors. Here it is,
As for ranged, a simple and easy solution has been suggested a million times by now - reduce damage of ranged weapons so they don't spill over total armour, and give them a certain piercing percentage to compensate.