Multiple Attribute Disorder
The warlock is a MAD class. Supposing that we want to cure this, it is pretty easy to do for the warlock. Making the Warlock an A class instead of a W class is pretty simple, and can actually be done in two ways.
There are at present 30 Cha/Int powers and only 15 Con/Int powers. This means Intelligence takes a much greater hit if the Conlock is implemented than if the Chalock is. Conversely, Cha becomes a much more important secondary stat for Conlocks than Con becomes for Chalocks.
The Conlock is my preferred variant, both because of what archetypes/races it promotes, because there are no other Con-primary classes, but despite that Int takes a big hit in utility.
This makes warlock a class for broody, charismatic goth-types.
Armor Proficiencies: Cloth
Class Features: Chalock, enduring despair
All powers that use Constitution as the attack stat instead use Charisma. Any mention of Intelligence in the power description of a formerly Con-based power is changed to Constitution.
You gain Dodge as a bonus feat. When wearing light armor you can apply your Constitution modifier instead of your Dexterity or Intelligence modifier to Armor Class.
This makes warlock a class for grim and humorless survivalists.
Armor Proficiencies: Cloth, leather
Class Features: Conlock, Luck of the Devil
All powers that use Charisma as the attack stat instead use Constitution. Any mention of Intelligence in the power description of a formerly Constitution-based power is changed to Charisma.
Luck of the Devil
When wearing light armor you can apply your Charisma modifier instead of your Dexterity or Intelligence modifier to Armor Class.