Great observations and questions, Sam!
At this point some of the classes I have are what I would call in 'Draft' mode, but most of them are reasonably well settled. Yes there are combinations of base classes that result in multi-classes of the standard kind, which is to say for example that a Brigand is a Fighter+Thief (in that order, meaning the Fighter aspect is emphasized).
As for the idea of "Prestige" classes, I don't really make that distinction, as I never really got that far into later editions of D&D to find out the specifics of what the D&D version of "Prestige" classes means, so I'm not sure if there is a similarity or not. But basically in the Elthos system all classes must be composed of one or more of the four base classes (Fighter, Thief, SpellChanter, and/or Cleric). Paladins are generally speaking Fighter+Cleric. That one is kind of up for grabs at the moment in terms of it's technical implementation, but the concept is that a Paladin is a Holy Warrior, who has powers that stem from the Merovingian Kings of ancient lore, who were said to be able to heal by laying on of hands among other things. I also like the idea that at some level (probably 3rd in my game) they get to summon an intelligent horse, and exercise other Paladinic Powers. These Powers, however, are not the typical mystic power that are cast by invocation, but are a different sort, and somewhat more intimate in that they are internal powers which the Elkron (deities) grant to Paladins when they achieve higher levels. That said, it's still in 'draft' so I'm open to suggestions.
The reason that some of the "Prestige" classes (I don't mind calling them that so long as it's understood that I don't mean that in whatever the D&Dish sense is, necessarily) have higher base requisites is potentially linked as well to the amount of Skill Learning Points that class receives and the Experience Base required to go up in levels. Again that needs probably a bit of ironing, so don't be too surprised if the class definitions for some of those change. The basic ideas, to the degree possible and sensible, is to have the classes balance out, but still leave the system flexible enough so that Gamesmasters going forward can create their own classes. If they balance them appropriately, and I intend to do so for mine, then players will be able to select between them without saying "gosh that one makes NO sense". But balancing can be a little bit tricky, which is why I do a rudimentary calculation and recommendation on the form that allows GMs to create new classes and offer that as a recommended suggested value for Experience Base.
Anyway, thanks for the thoughts! I will look over the classes again and see if I notice any ironing needed at this point... and of course if you have suggestions please let me know. :)
Thanks again!