Trevalon Moonleirion said:... I'm sure I could figure out some sort of "degree of success" thing that'd work to my liking for D20.
I think you're looking for Complex Skill Checks from Unearthed Arcana:
http://www.d20srd.org/srd/variant/buildingCharacters/complexSkillChecks.htm
That write-up is for D&D, but porting it to d20 modern won't be any trouble.