|No school like the old school, indeed!|
I thought I'd take a minute to summarize how I'm planning to handle this in Homebrew '82. My goal: Eliminate dice modifiers!
I admit that two major mechanics (fighting and spell-casting) do use a d20 as the "to hit" roll. Is it just nostalgia that I'm hewing close to Basic/1e D&D here, at least for the combat rolls? Cross referencing against the character's fighting ability and the defender's AC doesn't seem that convoluted to me. A single row on the character sheet is all you need to be looking at. Spells and miracles use the caster's INT or WIS as the "fighting ability" and the relative ease of the spell (i.e., caster's experience level minus the spell level) as the equivalent of AC. Temporary boosts in power can be thought of as enhancements to one's abilities, rather than abstract +X modifiers to a die roll.
For nearly everything else (ability checks, rogue skills, saving throws, contests), I greatly prefer the roll-low Xd6 system that I talked about here (see also cyclopeatron). The GM sets the difficulty level as the number of d6's to roll, and your ability score is the number you've got to avoid exceeding. Rogues get a higher "specialist ability score" for a few key skills, and that score advances by 1 with each experience level. I like that this also avoids the silliness of having two numbers for each ability (the 3d6 score and the modifier that goes from -4ish to +4ish), which I think unnecessarily infects some OSR retro-clones, too...
Want to see the probabilities for Xd6?
The color schemes illustrate the regions of absolute impossibility (gray), dangerously low chance of success (red), 50/50 (yellow), and near certainty of success (green). The bell-curve nature of these probabilities seems so much richer to me than those d20 core mechanic stair-steps.
But the thing that makes this system flow for me is the dictum of "No modifiers allowed!" I admit, though, that this rule has not yet been tested at the table! Will it hold up under the strong light of actual play? We'll have to see... :-)