If you've played D&D very long, and I assume anyone reading this blog has more than passing familiarity with the game, you probably know what I mean by character customization. Both Classic and Advanced D&D spawned a seemingly endless series of supplemental materials brimming with new classes, sub-classes, kits, skills, weapon mastery, combat maneuvers, character backgrounds, etc, etc, etc.
I understand the desire to play a particular sort of character. A good deal of the fun of D&D is in fleshing out your character and making him or her unique. Where I disagree is the notion that every variation on an archetype must be codified in game mechanics.
In the first place, all those extra classes, sub-classes, kits, and what-have-you rarely or never add anything truly unique to the character creation and development options. A swashbuckler, an archer, a barbarian, and a soldier all fit squarely within the fighter archetype. All can be realized in game simply by equipping and playing a fighter character in a fitting way.
Given that, why the enthusiasm for mechanically distinguishing sub-classes? My hypothesis is that it's a convenient excuse to hand out bonuses. Far more often than not, customization options, in game mechanic terms, are little more than bundles of bonuses. Attack or damage bonuses with certain weapons or in certain situations, defensive bonuses, hit point bonuses, saving throw bonuses, movement bonuses, bonus spells, bonus skills - you name it, there's probably a specialty class or an optional skill that grants it.
But why give players extra perks for playing their characters as they would have anyway? If I want my fighter to be a barbarian, he's going to use an axe whether or not he gets +1 to hit with it. If I want to be a swashbuckler, I'll deal with the disadvantages of light armor and play up the advantages, rather than demand an AC bonus while lightly armored. I don't need bonus spells to have my magic-user learn and memorize fire spells to play a fire mage, nor do I need special powers to play a cleric as a witch hunter or a scholarly monk.
True, you may say, it's possible to differentiate characters that way, but what's wrong with distinguishing them with special bonuses? Shouldn't a professional archer be a better shot with a bow than a plain old fighter? I have two answers to those objections. Firstly, it's a step down the road toward what I might call combat inflation. By name level, if not before, a fighter is already able to hit pretty much any AC more often than not, especially if he's got a strength bonus and a magic weapon. That +1 bonus may seem small by itself, but they add up, especially if you allow multiple modes of customization to stack. Add ability score adjustments to the mix, and you're looking at a character that's hitting a lot more often than the baseline for someone of his class and level. The inevitable breakdown in the rules that creeps in at high levels is brought a step nearer.
Secondly, by asserting that an archer should be better at archery than a vanilla fighting man, we're moving the game away from a class and level-based system and toward a skill-based one. Skill-based games are fine if that's what you like, but bolting it onto the class and level system creates some problems and redundancies. In the class and level system, a character's competency in all areas is represented more abstractly. Level advancement models the character's increasing skill generally, implicitly encompassing skill with all weapons and techniques he can employ. A skill-based system attempts a more granular approach; instead of a general aggregate of skills, it aims at tracking each individual skill separately.
It's not unrealistic to suppose that a fighter might train more intensively with a bow, and less with other weapons, but bolting on elements of a skill system to a class and level system doesn't model this very well. The archery specialist gets his bonus with bows stacked on top of his overall skill growth represented by his level - he gets to double-dip, as it were. He has an advantage with his bow, and he can use every other weapon allowed him with all the usual proficiency of his class and level. Meanwhile, the generalist fighter gains nothing for his choice not to specialize. He's worse than the archer with bows, and no better with sword, spear, mace, or axe. The same holds true for situational bonuses - a cavalier sub-class might have a bonus fighting from horseback, making him superior to a standard fighter when mounted, and no worse on foot.
One might be tempted to solve this double-dip syndrome by imposing a penalty on non-specialty activities. Consider, though, how often a character in your game is forced to use a weapon other than his weapon of choice. Not very? Then a penalty to other weapons really doesn't balance out a bonus with a preferred weapon. As noted above, you're just granting a bonus for using the weapon the player would already choose, and penalizing others that won't be used anyway. The logical result is for everyone to play some sort of specialist, everyone gets a bonus, and the baseline level of ability gets bumped a step toward that inevitable breaking point.
All of this is not to say that I necessarily think all attempts to expand options are bad, but the urge to codify every possible variation has consequences to game play that I don't think are very often given full consideration. It may add a touch of realism and some extra bells and whistles, but at the expense of added complexity and bonus inflation that skews game balance. Is it worth it? Not to me, but of course, your mileage may vary.