I've been looking at the attributes in Basic/LL, because there's something about them that I've never quite been happy with. I remember that around the time I got into D&D, prime requisites (PR) were becoming quite controversial: a common complaint was that characters with high scores in their PR attributes were doubly rewarded for it, by getting an XP bonus and getting the bonuses of the high attributes themselves. I think that there's something to that: as I mentioned in an earlier post, I'm happy enough with random-rolling for character creation (in certain types of gaming), but the double-rewarding (or double-penalising) factor of PRs puts heavier emphasis on the dice than I like.
I don't think that just removing the XP modifier for PR is really an ideal solution either. Something that I noticed and thought odd even when I was new to D&D was that Fighters got a hefty benefit from a higher Strength as well as the extra XP for a higher PR, but magic-users got nothing from Intelligence that directly improved their magic, only the XP modifier. Ditto for Clerics and Wisdom, and Thieves and Dexterity (though a good Dex could certainly help a Thief's weak AC).
What I didn't know at the time was that this asymmetry didn't exist in OD&D. In fact, OD&D is highly symmetrical in it's attribute system: the first three attributes (Strength, Intelligence, Wisdom) are the PRs for the three classes (Fighter, Magic-User and Cleric respectively) but have few direct effects, while the other three attributes (Dexterity, Constitution, Charisma) have more effects on their own, useful to any class. In the original game, Strength didn't affect to-hit or damage. That seems weird to modern gaming sensibilites, but like many things D&D, makes perfect sense when properly understood as a highly abstract system. A level 1 Fighter, a level 5 Fighter, or whatever, means a certain level of fighting ability. That fighting ability can come from being a mighty scrapper, a cunning dirty fighter, or a student of the Eight Hawks school of swordsmanship; all that matters is that a level X Fighter is X good at fighting. There's an appealing transparency in that. Where Strength enters the picture is its role as PR, giving extra XP to a strong Fighter. That makes sense in context, too: if a Fighter has natural muscle power, he can more easily learn to become better at attacking than a peer who has to work around a lack of might and learn more techniques to compensate.
That's a little more minimalist than I want, though. I chose a Basic retroclone instead of an OD&D retroclone for a reason! So, if direct combat modifiers for high Strength are to stay in, and Strength isn't to both give that AND bonus XP to Fighters, removing the bonus XP is the only alernative. Of course, assuming that Fighter isn't the only class to lose the XP bonus for high PR (and it shouldn't be; Basic Fighter's don't need nerfed compared to other classes), then Magic-Users and Clerics (and Thieves, to an extent) are left with no class-related benefit from their PR attribute. The typical solution for this is to borrow a page from AD&D or 3.X, giving bonus spells for a higher spellcasting attribute. I'm not really sold on this either, because it tends to be a huge benefit at low-mid levels and very little of one at higher levels, and the same goes for bonuses to Thieving abilities for a higher Dexterity.
I finally hit on something when I combined this quandary with something I'd thought of a while back: using Intelligence for a all characters' XP modifier, regardless of class. Combine this idea with a house rule I saw on the Dragonsfoot classic D&D forum long ago: use Wisdom modifier with all saving throws, not just magic saves as in the rules as written. This creates a situation with something like OD&D's symmetry, but instead of having 3 PR attibutes with little other function and 3 non-PR attributes with more direct uses, you're left with 6 non-PR attributes all with direct functions, but some are more useful to certain classes than others, which helps keep the flavour defining the attributes and classes.
Strength: Affects to-hit and damage in melee combat. Most useful to Fighters, but helps anyone who gets up-close and personal sometimes (notably Clerics and Thieves).
Intelligence: Affects XP gain and therefore the pace of gaining levels. Most useful for Magic-Users, who are notoriously limited and fragile at low levels and powerhouses at higher levels.
Wisdom: Affects all saving throws. Most useful for Clerics – it helps the whole party if the Cleric resists a mishap and so can help heal or protect everyone else.
Dexterity: Affects AC and ranged attacks. Most useful for Thieves, who need all the help they can get with their poor AC when they have to get into melee, and favour ranged attacks because their AC and HP are low.
Constitution: Affects HP. Everyone wants this!
Charisma: Affects reaction rolls, and retainers/hirelings (often overlooked in old-school gaming).
This set-up also makes a lot of intuitive sense. Strength helps anyone in close combat, not just Fighters. Intelligence benefits anyone; even Fighters can improve in their skills by having knowledge of different fighting styles, the strengths and weaknesses of different weapons and creatures, etc. Wisdom obviously benefits everyone: who doesn't want better saves? When you consider Wisdom as described in 3.X – including willpower and general alertness – it makes sense that it could help against disease or poison (having the determination to survive), or to avoid blundering into a trap, and various other non-magical threats.
One effect of these changes are that the spellcasting classes seem much less closely tied to their PR attributes, Intelligence and Wisdom. Magic-Users get XP modifiers from their PR attribute just like normal, so their situation isn't much different; Clerics are quite different though. The first instinct of a D&D veteran is probably to rail against this, but I'm not sure that it's such a bad thing. Clerics with high Wisdom just become more survivable, not more magically potent, and I quite like the fact that since their magic comes from “on high”, they only get more of it through their experiences: Intelligence can help them learn from it, Wisdom can help them survive it!