The many, many subsystems of D&D-based systems irks me. This is probably from not playing D&D-based games for a long time, and playing GURPS. GURPS has a very consistent rolling system - you roll low for skill checks, roll high for effect. Want to hit a person? Roll low. Want to kick down a door? Roll low. Want to do damage? Roll high. Want to see how much this guy likes you? Roll high.
D&D - especially AD&D - is a real mishmash of resolution systems. It doesn't really have to be, though. D&D is very consistently "roll high" in its basic checks - to hit, damage, reactions, stat generation, saving throws. Here is one subsystem - opening doors - that could easily be changed to a single approach.
This was sparked by Doug Cole getting an (incorrect) epiphany during our S&W game. He said, "Oh, so Open Doors is based on your ST bonus?"
No, it's not.
But it could be.
Using S&W Complete as a base:
Open Doors: Stuck doors open on a 5+ on a 1d6 roll. Add your Damage bonus or penalty to this roll. Locked or especially badly stuck doors may require a 6+. Easy to open doors may give a bonus of up to +5 (automatic for ST 3+). Magically held or locked doors, heavy portcullises, and bars that need bending may require a much high roll: 7+, 8+, or more. If multiple PCs cooperate, add their damage bonuses together. Normal sized doors generally only have room for one character, but very big doors or portcullises might have room for 2 or more!
Example: Weak Willie has STR 4, and a -1 damage modifier. He needs to roll a 6 to open a normally stuck door. He cannot open a locked or magically held door at all. Strong Sam has STR 18, and needs only a 2+ to open normal doors. A magically held door that needs a 8+ would still open for him on a 5 or 6!
This more-or-less matches the Open Doors numbers for ST. It gets rid of a stat line entry (you don't need an open doors roll) and as long as you know your damage bonus you know what to roll for a given door. DMs can write door numbers pretty easily, too. "Door (5)" or "Door - Magically held (7) or Weakly Held Door (3)." You can handle bend bars/lift gates the same way. Just give them a number. No more lookups, no more "what's my Open Doors roll? What's my Bend Bars roll?" - it's just "roll 1d6, add your STR damage bonus."
Games like AD&D, though, don't take to this system very well, because you get situations like STR 16, 17, 18, and 18/01-50 all having open doors of 1-3 but damage bonuses of +1, +1, +2, and +3. For a game like thatm you might want to just replace the system with the one above, or use the "to hit" bonus, with a minimum of a 1 in 6 chance to open normal doors. Since to hit goes from -3 (and you've put in a floor of 6+ always succeeds for a normal door) to +3 (which matches the 1-5 of 18/00) you're going to get consistent results.
Anyway, that's one small change you can make to start to put D&D-based systems on a consistent "roll high" basis, and get a scalable and easy to remember system out of the existing damage bonuses built into the system.