As I've been noodling over the list of available classes in my homebrew Frankestein 3.5 OGL system, I've decided that I want to at least spell out the less magic option, even if I don't decide to use it. So, for that option, I've removed all classes with a spell-casting progression or psionic power progression, and I'll be using d20 Call of Cthulhu style magic and psionics. Magic in this system works pretty much exactly like Incantations do, so in theory they're open. In practice, of course, I'd have to convert literally every single spell I'd be interested in using. So I'll probably just refer to my books and not post those rules.
This change really gives me the feel and tone that I want from my game, but the cost to get there is simplicity of house rules. In all honesty, in order to get there, I probably need to actually post all of my allowed classes so I can at least have them all in one place. Bleagh. That means work coming up with a document that has all of them, either online or as a pdf.
The sideline here, though, is that in thinking about this, I've revisited my class list to make sure I have sufficient variety. I actually do, but I have that in part because I have redundant classes. Different takes on the same archetype, or different interpretations of the same idea.
In general, in D&D, the classes work as four categories embodied by the "classic" four classes: divine caster (cleric), arcane caster (wizard), sneaky skill-user (rogue) and frontline combat guy (fighter). Most of the rest of the classes operate as hybrids of some degree or another, or as alternates. For example, the ranger is a fighter/rogue hybrid, the paladin is a fighter/cleric hybrid, the bard is a bizarre wizard/rogue hybrid with some other stuff thrown in too. A few other classes defy easy categorization; the monk is, like the ranger, a rogue/fighter hybrid, but with a completely different flavor (as is the swashbuckler), the sorcerer is an alternative to the wizard (for that matter, so too is the warmage, the wu jen, the warlock, etc.)
You could possibly also create a third axis here, with psionics; the psion as the psionic version of the wizard with the wilder as an alternate, and the psychic warrior and soulknife as fighter hybrids in two different flavors, and Complete Psionic creates other hybrids as well, including a rogue/psion hybrid, a cleric/psion hybrid, etc.
The differences between them from a game standpoint (not a flavor standpoint, but a role-protection standpoint) start to become extremely fine after a while. Take out the psion, divine and arcane caster options, and I'm mostly looking at fighters, rogues, and various alternatives and hybrids to those two roles. Some of the classes swing a little bit towards the other classes, but since they can't have a caster or manifester progression, they can only do so much. Add in third party material, and what I've found is that while I've got a lot of options, I've allowed a number of redudant classes.
As an example, I've allowed the rogue (from the SRD), the ninja (from Complete Adventurer), a different ninja (from the Rokugan Campaign Setting) and the assassin (from Freeport.) I can probably split hairs enough to have two classes that are significantly different here, but four is not going to work. The assassin (from Freeport) is basically a slightly darker version of the rogue, while the two ninjas are rogue/monk hybrids. While I don't have any problem with a player using the rules of any of these classes, I find that I do have a problem with saying up front that all four of those classes, which really just create a narrow spectrum between them, are all included in the campaign setting.
What I anticipate doing is allowing the rogue from the SRD (possibly beefed up with some assassin abilities as alternatives on the rogue abilities list for a more a la carte rogue that could be nearly the same as a Freeport assassin), and then work on hybridizing the two ninja classes and making sure it has sufficient separation from the new rogue.
This isn't the only example of where I'll need to do some rationalization work here; I've got two alt.monks (the survivalist from Freeport and the Defender from Midnight), a few contenders for a swashbuckler archetype (probably best hybridized and fused there as well), several contenders for the ranger archetype (although done in such completely different ways that I think I'll end up with a few options allowable there, and I'll also add in a few alternate weapon specialties and non-spellcasting options for the base ranger as well.)
Anyway, while I'm kinda excited about the prospect here, at the same time, I'm surprised at how much work this is no doubt going to end up being. Bleagh. Major house rule city.
It does give me an opportunity to at least present all the houserules cleanly; I can integrate the Pathfinder skill system right into the class descriptions, for instance. But, it'll be a pain to do the work.