Skill Throws for the Adventurer, Conqueror, King System

I've recently become a huge fan of Autarch's Adventurer, Conqueror, King System that takes inspiration from DnD B/X and the Rules Cycolpedia and came up with an idea for handling "skill throws".  This system can ignore ACKS proficiencies or work side by side with it.

Skill Throw Progression

Level          Throw
1 - 2             15+
3 - 4             14+
5 - 6             13+
7 - 8             12+
9 - 10           11+
11 - 12         10+
13 - 14           9+

Then add Backgrounds as they appear in 13th Age.  A background is a bundle of skills and the player may ask if it could apply to the situation involving a Skill Throw.  A character has 8 + Intelligence modifier in points to distribute amongst their backgrounds and may not allocate more than 5 points into any one background.  If the GM is concerned that a player takes a background like Cat Burglar that would grant thief abilities, then allow 5 background points to grant access to one thief ability.  A background is then added to the d20 roll for the Skill Throw.