Wow, this is a great idea. Stat + 1/2 level + 5(trained) +5 (Skill Focus) is simple to keep track of, and will help with NPC generation on the fly. I also like the idea of having feats and talents give rerolls and unlock additional uses of the skill.
If this system doesn't significantly alter DCs for most skills, I'm strongly considering it for my True20 game.
Let's see:
Level 1 guy with no stat bonus, and Skill Focus:
In D&D: 4+3 = +7
In SWSE: 0+5+5 = +10
Level 5 guy:
In D&D: 8 ranks + 3 Skill Focus = 11
In SWSE: 2(1/2 level rounded down) +5 trained + 5 Skill Focus = 12
Level 10 guy:
In D&D: 13 ranks + 3 Skill Focus = +16
In SWSE: 5+5+5 = +15
Level 20 guy:
In D&D: 23 ranks + 3 skill focus = +26
In SWSE: 10+5+5 = +20
Interesting. It starts out higher for the SW guy than in D&D, becomes very similar for the mid levels, and then D&D finally pulls away at Level 20.
I think this would be very easy to adapt to a standard system, provided one could figure out which skill uses were only for "trained" characters.
I can't wait to see what happens to attacks of opportunity...