So we’re playing OSE, using ascending armor class. When attacking, players want to roll high. And when rolling saving throws, players want to roll high. But when making ability checks, they want to roll low. Now, I’m not opposed to ‘roll low’ at all, but it seems like with just one of three core mechanics inverted, players often get confused and have to double-check the logic almost every roll. I don’t think having mixed logic adds anything awesome or old-school feeling to the game, just confusion.
Now, we could go full descending rolls, and that’s fine for DAC; but then ‘lower numbers are better AC’ becomes a thing, which I have always found unintuitive (even back when 2E was the current version). And saving throws are still ascending…
So how about making ability checks ascending too? Just subtract your ability score from 21 and that’s your target number/DC, modified for difficulty by the DM. I imagine this has been done before, but I haven’t ever seen it mentioned.