In fact I don't feel like the Prestige Classes should have skills associated. Anakin and Han Solo are both Ace Pilots, but their capacities and skills are totally different. There are many ways to be a Bounty Hunter, they are not all cut by the same pattern.
I think that the Classes give the Heroes the necessary background, and the Prestige Classes give the high specialization. If Han Solo is the way he is is because his youth, the time he learnt the base of all the things he can do now. One clone pilot could exceed to be a Ace Pilot too but doesnĄt have to know how to bargain because he is a soldier and nothing more.
-Noble: You were born in upper class. You have the maximum skills because you have the best education you could achieve.
-Scout: You have worked in nature, maybe like a settler in a colony, maybe because you are from Rodia or another planet with old technology. You have a lot of skills because in the wilderness you need to be smart and survive.
-Scoundrel: You were born in the lower class, and because that you had to learn how to make your own space. That's the explanation of that variety of skills you can learn, but not the number of them.
-Soldier: You have been in the military since you were youth, and you have learned all you needed there to survive. You know how to kill, to repare your own equipment or your own body. Since you have received the education of a mere soldier, you don't know how to be really sneaky, or how to talk in public (in the battlefield it matters more the militar rank than charisma).
-Jedi: You were taken in youth age by some force user organization and learn his ways. Since you have study the Force, and all that matters is the Force (no idea why lot of people think Jedi are a sect. Yes, a good one, but a sect in the end) you should know how to use the force, but not much more. And if you don't know UtF skill at level 1 is because you will be the worst Jedi ever.
Yep, Star Wars is very classist. But that doesn't have to surprise us. In the line with this, I think that every multiclassing should be adequately interpreted. A PC multiclassed to Soldier should have a (minimum) militar instruction to learn the basics. A PC multiclassed to Scout should focus to learn tricks to survive. Multiclassing to Noble should mean a try to getting closer to the high statements of the society and learn from them (the same with Scoundrel and the fringe) and Jedi should reflect and education by a force user or, at least, an autodidact approach to the Force.
Prestige classes are only continuations from these archetypes.