My first step was to take each of the four number sequences and give it a "class" designation -- class A skills end up at +15, class B ends up at +13, class C at +9 and class D ends with +8.
Then I simply organized each into piles. For example, for a Lawful thief:
Class A = Hide in shadows*; Climb sheer surfaces*, Find trap†, Disable trap*
Class B = Backstab, Sneak silently*, Pick pocket*, Pick lock*
Class C = Disguise self‡; Handle poison
Class D = Forge document*; Read languages†
So, if you know which class a particluar skill is for your thief, you have a smaller chart to look at to obtain the correct bonuses. I did this for all three alignments of thief and it seems pretty straight forward. Again, whether or not it's an "improvement" I'm not sure. It does look pretty simple on paper.
If I could figure out how to upload it, I'd share it.
EDIT: In retrospect, I think my use of the term "class" is a bad one. Perhaps I should have called it "type A" and so on...