....
However, to include this is a rather good idea I think! It would have to be a subtle thing, and perhaps give you some penalty.. Some examples:
Horsemaster: A normal horse can turn into "Spirited" if left in your inventory for 1 week (or more), you could also improve the "Stubborn" to normal, and then on to "Spirited". However, I don't think you should be able to train them into "Champion". If so it would have to have a big penalty. I can not think of any suitable penalty for this, maybe lowering the weaponpoints gained each level by 5?
Bureaucrat: You can claim more taxes from your fiefs, say 10% or so, but slow down the prosparity growth. So it would pay of in the long run. Maybe some other penalty, like random revolts in your fiefs, or the population not liking you..?
Weaponmaster: You get 5 extra (or 10, or whatever number) extra weapon points each level, but you can not upgrade riding further then 5..?
Prisonmaster: You can hold more numbers of prisoners per skillpoint, and get more money from them... Cant think of a penalty..
Lightfoot: You have a greater chance of escaping from captivity, you have a greater chance of sneaking in to an enemy city without being detected.. cant think of a penalty.
Masterchef: You gain more morale from food, but you also consume a lot more food. Good for big parties with lots of inventory space.
[Insert name] You need less food but you also gain less morale from it. Good for small parties with little inventory space..
[Insert name]: You gain +25 in base morale (so its 75 instead of 50) but you pay double wages, or 50% more, or whatever.
Investor: When its time to pay the weekly wage you get a bonus 5% on the money remaining (say you have 12000, you pay 2000 in wages, that leaves you with 10000, then add 5% (500) and it leaves you with 10500). Cant think of a penalty.. maybe something morale related...?
Scholar: You read books faster, need less int to read them. The price of books get higher cause the bookseller see that you are interested (since you are, you are a scholar..) so he figures he can rip more money from you..
I could probably think of more ideas, a bit tired now.. 5 AM... and yes, they way I put it out here it is not balanced, I'm just throwing out ideas and pretty much all the ideas have numbers that you can alter to balance things out. Some ideas, like Lightfoot are rather silly, but at least its subtle : )