Bront
The man with the probe
I think first you need to fix synergy, because it's easy to get the equivilent of a feat with a single skill. I personaly think that +1 per 5 makes more sense than +2 at 5.
Next, for scale, I think something along the lines of +1/+1 that increases every 3 levels after that would be appropriate. I guess you could do +2/+2 and a +1/+1 increase too, but that seems a bit powerful.
Keep in mind, part of why these feats exist is to allow someone to get a higher than "Max" bonus at any level. Some skills this is more useful for than others, particularly at certaint levels (Early concentration for a Psion, Tumble is very nice at a particular bonus for moving in combat, Jump can get... fun at high bonuses, etc). Rystil Arden has made a character who can get a +38 in diplomacy at level 3 (A half-elf Enchanter/Psion/Warlock), imagine where that could go with scaling bonuses on the appropriate feats?
Next, for scale, I think something along the lines of +1/+1 that increases every 3 levels after that would be appropriate. I guess you could do +2/+2 and a +1/+1 increase too, but that seems a bit powerful.
Keep in mind, part of why these feats exist is to allow someone to get a higher than "Max" bonus at any level. Some skills this is more useful for than others, particularly at certaint levels (Early concentration for a Psion, Tumble is very nice at a particular bonus for moving in combat, Jump can get... fun at high bonuses, etc). Rystil Arden has made a character who can get a +38 in diplomacy at level 3 (A half-elf Enchanter/Psion/Warlock), imagine where that could go with scaling bonuses on the appropriate feats?