As a quick review, here are the various class features you can pick from:
- Combat bonus: +1 to attack and damage; increases by an additional +1 at 4th and 8th level.
- Sneak attack
- Affinities: start with 1, get an additional one a 3rd, 6th and 9th level.
Keep in mind that the Shadow Sword class is not customizable; it stands alone as the only class that cannot be altered. Also, keep in mind that the Outdoorsman's class abilities all count as minor class abilities. He essentially has three minor abilities rather than one major and one minor ability. It's entirely possible that the animal companion is over-powered in this case, but I'm going with it anyway, because if so, it's not overbalanced by much, and it's pretty traditional.
- +3 to any skill
- a single affinity
- an additional +3 to AC
- an additional +1 to attack and damage with one weapon type only (light, medium, heavy or ranged)
- an animal companion (note that there is no official rule on what an "animal" is from the monster list, so GM discretion is at play. If a GM wants to count an imp as an animal, and treat this minor bonus as equivalent to some kind of familiar, he can choose to do so. I would.)
The basic classes are, as a reminder, as follows:
- Fighter: combat bonus and +3 to Athletics
- Rogue: sneak attack and +3 to Subterfuge
- Outdoorsman: +1 to ranged attacks, animal companion, and +3 to Survival
- Expert: Affinities, and +3 to Knowledge
- Shadow Sword: a suite of unique abilities; the Shadow Blade, and a limited +3 to Subterfuge (only when combined with DEX.)
How would I make a Sorcerer, Warlock or Witch, for instance? How about pairing the single affinity (Sorcery) with a familiar (an imp would be my choice although there are other great options too) and +3 to Knowledge to better learn spells?
What would I call a character with Combat Bonus and a +1 to ranged weapons? A Gunslinger, Sharp-shooter, or Sniper, maybe. With another weapon type, maybe call him a Weapon-master or Gladiator, or he could be a Defender by taking Combat Bonus and +3 to AC.
Another take on the Outdoorsman archetype (and why not, let's call him a Ranger!) could be to have the Combat bonus and an animal companion. A Scout could have +1 to ranged weapons, +3 to Survival, and a single affinity for Wilderness Survival. Both deviate from the Outdoorsman sufficiently to feel quite different, yet not enough to feel like a totally different archetype, just a different take on it.
You could even make something like a Bladesinger-style class by giving a character the +1 to medium weapons (so he can use a longsword), an affinity for Sorcery and a +3 to Knowledge. Or you could tweak that by making it +3 to Subterfuge instead, and get a character not unlike the Gray Mouser (as an aside, I'd see Fafhrd as a Fighter but maybe with his own +3 applied to Subterfuge rather than Athletics, maybe.)
Alternatively, you can do some unusual things without even changing the classes. An Expert can be a Wizard or Mage by taking Affinity and making it Sorcery every time he gets a new affinity (by 9th level, he'd have it 4 times, allowing him up to 3 rerolls on any failed check involving sorcery).
One of the beauties of this system is that it's so flexible. I don't mean in the sense that you can create almost anything you want (although you can) but in the sense that it doesn't make niche protection a primary design goal. In other words, all characters, as they advance in level, manage to be competent across a broad range of adventuring tasks, and the class abilities are actually somewhat modest (and become relatively moreso as the character advances.) A 5th level fighter, for example, will fight with a +7 to attack and +2 to damage, but a 5th level Expert with the same strength will still fight with a +5 to attack. While I don't necessarily recommend that a 5th level expert pick a straight-up fight with a fighter, at the same time, it's hardly inconceivable that he'd win if he did. (Of course, more likely he won't have the same strength, since Experts are more likely to focus their traits on MND over STR.) Any character can potentially sneak around successfully (although clearly a rogue with +3 to Subterfuge, or an Expert with an affinity for Stealth would be at an advantage in doing so), and character can learn to cast spells (although a character with an affinity for Sorcery would be a safer bet to do so), etc. Anyone can do anything with a reasonable chance of success, and the class bonuses, while nice, are not requisite.