Sorry for doublepost, but this deserves one of it's own.
Before I say anything else, I have to ask: Will we be able to train the followers Galia/we ourselves gain from Leadership to higher levels? If so, will they still count as taking up that slot for the purposes of the leadership feat, or will the leadership feat effectively be a recruitment system?
I'd really like a revamp to the training system. While it's not going to make much of a difference at the moment, once we have a lot of followers it's going to be fairly hefty. Prepare for info-dump/opinions of the most opiniony nature.
So, thing is, personally I consider around level 3 to be average in the world. It just seems silly for the 60-year old farmer who's lived on a farm his whole life to be worse at farming than the 30 year old veteran soldier who happened to take it as his Profession skill and has participated in a dozen campaigns and only been home maybe twice. Skill usage should, in combat-minimal environments(read: not near the PCs), give small amounts of experience. A farmer-boy being at level 1 from age 18 to his deathbed at age 58 is just ridiculous. I'm not even gonna get into my internal debate on exercise to improve physical stats(and no, the every fourth level is not what I'm talking about, damn it).
Anyway, point is, NPCs should probably level up over time if you think about it logically in the background environment. Elves and dwarves can get really good at smithing/magic or whatever partially because they live a long time, while humans can because they're naturally adaptable and have a knack for just about everything. It also helps explain why Orcs and other short-lived races tend to be warlike; warriors don't tend to live long anyway, and since they don't live all that long, it's hard to get good at farming or fishing easily. It would also thus explain the stereotype that such races don't usually have good equipment; their smiths can't get experience as easily. Add this to a naturally savage temperament and a culture that has regressed/failed to rise from it's barbaric roots, and tada, fluff/crunch inter-relations.
However, that has nothing to do with the PCs, really, and I'm not sure how my train of thought got there. Doesn't really matter. For training: Thing is, it's kinda silly the way it works now, and while it makes sense in some ways, particularly for magic(and I would advise it stay that way for magic, as it makes sense and helps explain why there aren't mind-blowingly powerful mages everywhere), it is...less so, for non-magic classes. And even for similar magic classes, I would think that it should be a bit more, depending on how similar it is; for example, a Favored Soul being tutored by an experienced Paladin should probably give a bit more than a Paladin being tutored by an experienced Cleric. A Crusader would probably learn more from a Paladin than they would from a Warblade, but more from a Warblade than they would from a Fighter, despite them all being melee classes. A Scout could easily be taught by a Ranger or Rogue(or especially a multiclass Ranger/Rogue, get to that in a sec), while a Spellthief would probably learn from a Beguiler or Bard decently well too. I'm thinking it should be handled more on a case-by-case basis, with NPC classes automatically counting as max similarity if they're in similar categories(Expert being taught by a Rogue, Warrior by a Fighter, or Adept by a Druid, as examples). For this purpose, I would say Aristocrat should count as a PC class(harder to train the snotty little bastards unless they're just becoming Knights or something), but when they gain that 500 Exp they become level 2 in a PC class in addition to upgrading their base Aristocrat class into a PC class, due to their untainted blood the original strength and importance of Aristocrat NPCs in most settings. Part of this is because some classes are very generic and thus having an Archer-type Fighter be better at training a Power-Attack&Shock-Trooper Fighter than a Power-Attack&Shock-Trooper Barbarian is just silly.
Now, onto multiclass training stuff. To sum it up, so I don't have another rambling paragraph; case by case, use logic. A multiclass Paladin/Fighter/Samurai should be able to teach a Warrior or a Fighter just as well as if they were an equal level single-class Fighter. Similarly, if their Prestige Classes fit, they should be able to train them that way as well.
However. For Complexity Addiction, and because by itself that would allow for rather dumb combinations, like a Fighter 4/Paladin 3 training a Fighter 5 to be a Fighter 6, which is what I believe you were trying to avoid, I would like to add a new Skill to the game, that all classes have as a class skill: Tutor (Int). Treat it like the way Craft skills are handled, typically on a weekly basis, with penalties if their level is too high or too near to your level, or higher than your individual class levels in what they're trying to learn. Can get bonuses if Masterwork tools are available (like, you know, actual training facilities), get minor penalties for teaching large numbers at once, can even specialize in it since you could take Skill Focus. Makes it so that Teacher is actually a profession within the game. Other things could apply based on logic; A Druid might get a bonus equal to her Wisdom score when teaching someone in Nature(divine) magic, rather than her Intelligence, a Sorceror might get Charisma, etc. If you are able to bring in or work with someone more suited to certain aspects of the teaching, might be able to offset penalties or give small bonuses(like if a Wizard and a Fighter worked together to teach a Hexblade, they would be much better at doing so together than individually).
Some classes would be harder or require specific tutors to teach than others due to their nature, like Artificers(in order to train, you have to make items, in order to make items, you have to spend EXP, in order to gain EXP to spend, you have to train...) or Druids (who basically have to be brought into the fold by another Druid), just as examples. All case-by-case things, to avoid having to do truly stupendous amounts of work. Might even just make it a subset of Craft, if you wanted, with specific rules since it had to do with EXP.
Either that, or making it so I can bloody well keep teaching Ganron without being at such a severe penalty as I am now. Right now, current rules, I cannot train him at all, and if I were to do so, it would be really ridiculously slow compared to if he had just a single level of Warblade or Swordsage or whatever.