(I make no apologies for these ridiculous nerfs.)
In the Veins, cultures almost never use Platemail.
The Weeping Knights of the Knotsmen and some Duregar may make some occasional use for expeditionary purposes.
Those guarding fixed positions inside cities may have plate and large shields.
No-one else ever will.
Squeezes are simply not accessible to anyone in plate and are difficult to anyone in chain.
Sumps and Swimming are made so difficult they verge on suicidal. The armour drags you down and gives you hypothermia if you survive.
No-one wearing plate may attempt a climb of hard, very hard, or above.
If any PC is wearing Plate then when the party rolls encounter dice, a 1 causes a normal encounter, a 2 means the plate has gone wrong, roll a d6
1. Rusted. Now loses 1 AC per week unless cleaned for d4 hours a day.
2. Dented. A random limb now has limited extension.
3. Noisy. Squeals all the time.
4. Trapped. You are stuck in a narrow space and need friends to free you.
5. Slow. journey will take x2 as long.
6. Freezing. Roll for hypothermia.
Or roll on this much more fun chart.