Thinking about the armor staking, I think it's not a real problem. In fact, the plate armor already includes its padded underwear when giving DB bonuses. We can imagine that a padding+mail+plates will include rather 'light' model of each armor as even a very stout warrior can carry only so much weight, and adding full undergarments, full chain and a normally thick plate armor will weight something like 60 kgs...
Something I cannot concur.
Reenacting a knight of the middle 13th century I wear a full version of each type of armor.
My complete infantristic outfit consits of normal clothing including leather boots, full padding on the head, the complete torso, the arms and the legs, mail coif, shirt with long sleeves, gauntlets and "trousers", a plate helmet, a shield and a weapon (either spear, axe or sword) plus a dagger.
The overall weight is 48,7 kg (approx. 110 lbs) and is burdensome but manageable to wear in combat (as it was done historically). I plan to add a surcoat with plates sewn inside on the chest, abdomen and the back, adding an additional 6 to 7 kg to the overall.
Don't fall for the trap of a lighter version of armor, there simply is and was no such thing!
As I said before, I can live with the mechanics provided by HARP.