But I won't get that much into it. HackMaster did find (really, find, I don't think the rule originates there, but is rather something somewhere hidden in AD&D...) a nice way to make this an achievement per level, without inflating ability scores. Each score gets an additional number between 1 and 100 (roll 1d100) with character generation (like they used to allow with STR). With every level those numbers will increase, but different for every ability score, depending on the main focus of a class (fighter, thief, cleric, wizard). As soon as a number exceeds 100, the ability score goes up one point. Every point over 100 is kept and you go from there to get the next 100 points.
To translate that from HackMaster into D&D is very easy. We use it in our game for some time now and I always wanted to fix it in digital ink. So here it comes:
Ability Score Advancement per Level:
STR +1d4If you allow Echoe (see Hacking Hackmaster, Part 1) to it, you'll make your players happy. If you need a few reasons to get rid of Charisma, maybe you'll find some in Hacking Hackmaster, Part 2.