Why not add a Warding keystone?
as it is right now there is more offensive keystones than actual cunning keystones for supports.
So why not add a warding keystone?
Here's is a rough implementation of one.
Cunning tree:
"Illuminate-
+1 to max ward capacity does not include pink wards
all trinkets Charge 20% faster
Warding items gain the ability to recharge wards for one every 60 seconds holding a max of 3 wards."

What do you think? it could be toned down if it was to be implemented as a more accessible version in tier 1 or tier 2