ability scores as potential rather than realised ability. I'm trying to expand on that idea by looking at how one might export the functions of AD&D 1e's ability scores to character class and level. (Briefly: the idea here is to keep the game more focused on these latter qualities because of verisimilitude and fairness. It makes sense that skill is decisive and reducing the impact of random factors in character creation has long had an appeal.) I chose Strength to start the discussion because it's the first in the book, but also because its functions in AD&D are widely spread. In this post, I'll consider Intelligence and Wisdom.
For most characters, the effects of Intelligence are fairly trivial. Gaining proficiency in additional languages is very occasionally life-saving, but in the most part the multi-lingual demi-humans already know the most common of the uncommon tongues. Wisdom is fractionally more important, providing a modifier to a range of mind-affecting saves.
The rest of the affects of these abilities relate to the spell-casting classes and that's why I'm taking the two in one stride. Magic-users have a limited ability to learn spells dependent upon their Intelligence score. Clerics run the risk of spells failing if they don't have sufficient Wisdom, but gain bonus spells per day for having a high score. Both classes have ability score requirements to access spells of 5th level and above.
Taking Intelligence and Magic-users first, it seems fairly straightforward to move the maximum and minimum spells known at each spell level over to a function of character level vs. spell level. In other words, each time a magic-user acquires a new level of spells, she would be able to learn no more than six spells at that level. As the magic-user gained levels from this point, her maximum spells for that level would increase. The chance to learn spells is less obvious, but I think that the rules would be clearest if this chance was uniform for all spells and rose as the magic-user gained levels.
It's tempting to simply bury the effects of Wisdom when it comes to the Cleric class. However, I think redrawing the spells/day table to show one bonus spell at each level obtained (e.g. two first level spells per day at first level, three first level spells and two second level spells per day at third level) and imposing a risk of spell failure for the highest level of spells obtained might be the best way forward.
Finally, for the effects that apply to all characters, I think the saving throw modifier can simply be dropped while maximum languages spoken could be made a function purely of level for player characters, with age being used as a proxy for Common Men.