Skills in AD&D 1

I got to play some AD&D 1st ed again this past weekend.  The boys are really enjoying it.
But the one thing that now feels awkward are ability checks.

Back in the day if we wanted to do something that would require a "skill check" we would roll a d20 and aim to roll under the ability in question.  Easy and it worked for us till the 1st ed Proficiency system came along.

Looking back I remembered something.  I hate the 1st Ed Proficiency system.

I think what I want is something more simple.  AD&D isn't really about what skills and how many skill points you have.  Your skills are defined by your class or race and Ability scores are key.

So I am thinking of taking some ideas from d20, Castles & Crusades and even a little bit of D&D4.

Skill checks will still be Ability checks.
Instead of the roll under mechanic, I am going to use a d20 style Difficulty Classes. Since 3.x d20 and AD&D1 make the similar assumption of 20 levels I think the numbers are good.

Abilities will use their default modifiers.  So 0 +1, +2 or +3 (or negatives as the case may be).  Additionally characters will add +1 per level.  I *might* cap that at 10th level.  I have not decided yet.

Borrowing from Castles and Crusades each character will get two Primes.  These will be the same as the Prime Attribute for their class. Humans will get one extra. Primes will add +2.

So a skill roll then would be like this.
A 1st level Cleric with an 18 Wisdom is making a Spot check.  Wisdom is his prime.
His chances are +3 (wisdom) +1 (level) +2 (prime) for a total of +6.
That might sound like a lot, but a Cleric in 3.x with Spot as a skill would get +4 Wis and +4 for the skill for +8.

I might also give each character a chance at a signature or trained skill.  Something very specific that they get and extra +1 on.  So my cleric in the above example might have Religion as a signature skill, and get an extra +1.

I think this will work fine to be honest.  Course if I wanted that "old school" feel I could put it all in a chart.