I'll try to address some of the issues this system might bring up later in the post, but for now let's spell out exactly what the table I'm imagining might look like:
*IMPROVEMENT TABLE*
2-9 = A single New skill of any value or new skills with value no greater than 20K.
10 = Increase the player's MA or AV by 1 point or a single New skill of any value or new skills with value no greater than 30K.
11 = Increase the player's AG by 1 point or New skill(s) with combined value no greater than 40K.
12 = Increase the player's ST by 1 point or New skill(s) with combined value no greater than 50K.
Note : the new skill(s) a player takes must always come from the categories he has normal access to unless the Improvement roll is a doubles.
Alongside this some skills would change in the value they add to a player's TV, summarized below:
10,000gc = Fend, Kickoff Return, Pass Block, Pro, Shadowing, Catch, Sprint, Sure Feet, Diving Catch, Hail Mary Pass, Nerves of Steel, Dump Off, Grab, Thick Skull, Strong Arm, Extra Arms, Disturbing Presence, Prehensile Tail, Very Long Legs, Horns, Big Hand.
20,000gc = everything not mentioned elsewhere
30,000gc = Block, Dodge, Leader, Guard, Piling On, Claw
Skills players do not have Normal access to and have to be gained by rolling doubles cost +10,000 instead of the flat 30,000.
As you can see, lots of things go into the 10K list, as this will encourage people to take two good skills instead of the same good (but boring) one or two.
For example, an Human Lineman rolls a Normal Improvement. He could take :
Block, adding 30K to his TV.
Wrestle, adding 20K to his TV.
Fend and Pro, adding 20K to his TV.
To me this perfectly logical. The Block guy is the better player, and the Wrestle guy is probably still better than the Fend/Pro guy. But this gives coaches the option to mess around more without being punished quite so harshly. At the moment there really is a right and a wrong way to build teams, and poor old skills like Pass Block don't get much of a look in.
Note that this doesn't increase the frequency of doubles skill access, and doesn't change how likely a player is to get any given skill. I don't like the stick of traits, that stops you taking certain skills. I much prefer a carrot system like this, that rewards coaches who try to build outside the cornerstone skills such as Block/Dodge/Guard. It also has a built in mechanism for punishing abuse of ClawPOMB. Note that some of the 10K skills are in that list because the only players who want them require a doubles to get them. E.g. NoS is a skill desired by catchers, and isn't worth 30K (the same as Block) IMO. I'd also say stunties don't have to pay the 10K doubles penalty. 40K for a Block Goblin ain't right.
Thoughts?
Then when he gets the improvement after Leap, give him your choice of two from Pass Block, Pro, and Shadowing. 
