"Ability checks with a d20 measured against a DC serve as the basic rule."I think that's a lousy way to handle ability checks. You have two different things varying: the ability and the DC (plus the die roll, but that's a given.) That's not even counting additional modifiers; we're just talking about the minimum needed for the core mechanic. And it gets worse, because it's obvious in the article he's talking about ability check based on ability modifiers: roll or point-buy your abilities, look them up on a table to get your modifier, add this to your die roll, and look up the target number of the task you're trying to accomplish. That's a whole lot of extra work.
Really, you only need one thing to vary, so you have two options:
- Make the DC equal to the ability (roll under system.) This ditches ability score bonuses except as situational modifiers or bonuses to other things, like damage. Super simple.
- Make the DC equal to the opponent's ability (roll over system.) If there is no opponent, use a fixed number. Target 20 does the fixed target straight across, Epées & Sorcellerie uses AC or Dex of the opponent as a target, but there are other possible variants.
(EDIT: I screwed this part up the first time. TWO different errors, and ironically it's because I made the same mistake I accused Mearls of making. Corrected now.)
- Generate ability scores in the standard way (3d6 base, but those who want 7d6 drop four or standard array point-buy or whatever can do so.)
- To attack or change/affect your opponent, roll d20. Result => opponent's appropriate ability score means success.
- For saves against physical danger, add your own ability score to the d20 roll and beat target 20 (i.e. average character saves a little more than half the time.)
- For class abilities, add level; for saves against spells, add opponent's level to target.
Clever players can come up with ways to get a bonus from another ability; this is where ability modifiers come in. For example, a fighter could attack normally (d20 + level) or slam an opponent with a shield (as normal, but add Str mod.) Optionally, feats or skills would let you add such bonuses in specific situations: Anatomy skill might allow adding Int bonus to d20 attacks. Any feat or skill list would be suggestions only; players and GMs could churn out an unlimited number of these using this one simple rule.
(EDIT: Had to correct the examples, too, to match the corrected rules.)