A couple of campaigns ago, as I was looking at all the different types of "bonus to X and Y skill" feats there were (frex: Alertness, Deft Hands, Self-Sufficient) I hit on the idea of having "skill specialization" feats that would grant a bonus to some specific use of a skill, such as using Handle Animal to "teach an animal a trick" or using Stealth to "create a diversion to hide".
I had also thought about restricting such feats to one such feat per skill, meaning that if there were several specialization feats available to boost a certain specialized task for a given skill, then the character could only ever take one of those. For example, for Use Magic Device there might be a separate specialization feat to activate a device blindly; to decipher a written spell; to use a wand, staff, or other spell trigger item; to emulate a race; and so forth. A character would be able to take just one these feats, but to the exclusion of the rest.
So, what would be an appropriate numerical bonus to make such specialized feats worth the cost of a feat slot? We would have to take into account the likelihood that a character might be taking Skill Focus for the skill (which would stack), and in many cases there will be an Alertness-clone feat to increase a character's bonus still further.
