Many people interpret rolls like Hear Noise, Find Secret Door, and yes, Find or Remove Traps as a skill roll (something you can do.) In contrast, I prefer to think of these as being related to the roll for a spike slipping or a trap opening, a category of roll I call situation rolls because they tell you whether the current situation changes. The difference is that you can in theory study to improve a skill; but should you really be able to study how to hear a noise or open a door? Or are you really rolling to see if a monster happens to make a noise while you are listening or if a door is stuck? I prefer the latter, and would like to excise skills completely except to grant a +1 at the most to appropriate situations.
But that leads to the question "what do we do about the thief class?" Thieves are definitely presented as having skills that improve over time. I'm musing about whether they can be recast without skills, just with situation rolls.
Thieves basically have six ability "bundles": cleverness (read treasure maps/magic scrolls,) climbing, manual dexterity (Remove Traps/Open Locks,) sharp senses (Hear Noise,) stealth (Move Silent/Hide in Shadows/Pick Pocket,) surprise attack (backstab.) They are actually grouped this way in Supplement I (Greyhawk,) although not with those six names.
We can actually combine stealth and surprise attack into a blanket "surprise" ability, which fits with my idea of recasting the abilities so that they aren't skills: give thieves an increased ability to surprise, as I did with the Trickster in my alternative class system, and make Move Silently, Hide in Shadows, Picking Pockets, and increased damage from a surprise attack something that happens automatically if a thief surprises a foe. You're no longer rolling to see if you successfully pick a pocket, you're rolling to see if you were unlucky enough to be noticed.
Hear Noise can be recast pretty simply as well, as monsters needing to be extra silent to avoid detection by thieves. I'd expand this to sharp senses in general, though, including Find Traps (which is not in Greyhawk, although it shows up in AD&D and BD&D.)
Climbing similarly can be recast in terms of slipping and falling, the way it's actually expressed in Greyhawk. We can thus just say "Climbing with gear requires an Avoid Accident roll (4 or less) to avoid slipping, or an Avoid Danger roll (5 or less) without gear on a surface with hand and footholds. Thieves can climb sheer surfaces with only the barest traces of cracks and add a bonus to avoid slipping, plus a bonus to any saving throw allowed to catch themselves before falling all the way to the ground." It's now a universally-applicable situation roll, instead of a unique skill roll.
The ability to read maps and magic, surprisingly, doesn't need to be a skill, either. Reading scrolls is assumed to be automatic for master thieves, but there's a chance of a reversed spell result. Reading maps can similarly be expressed as a chance of misinterpretation. I wouldn't express this as "Read Languages," though; I would restrict it to an ability to decipher clues in unreadable texts based on "I've seen a symbol or word like that somewhere..."
This leaves the manual dexterity bundle, which resembles skills even more than any of the other abilities. Still, Remove Traps can be recast, if you think about it this way: a small trap, like needles that dart out when you grab a door knob, is triggered by a specific action. Removing a trap normally does not involve the triggering action, but you roll for the chance of triggering the trap anyways. It's a Change Situation roll (2 or less on d6) with a +1 difficulty added to the die roll, with the trap being accidentally triggered on a 6+. Open Locks can be handled the exact same way, if we consider a result of 6+ being a chance of jamming the lock. Modify the target number for either roll by half the thief's level, or by the thief's hit dice (if using the d6-only magic-user's hit dice progression for thieves, instead of the d4 per level progression.) I would allow non-thieves to seek out and pay for training as a locksmith, trapmaker, or similar profession, which would give the same base chances without the thief's level bonus; this separates the skill (which is normally a binary yes-you-can/no-you-can't in OD&D) from the misfortune (can't pick lock/remove trap quick enough, chance of jamming or triggering by accident.)
So, here's my summary d6-only, de-skilled thief for OD&D:
- +1 Hit Dice every other level (as M-U;)
- minimum chance on d6 to surprise if moving stealthily = hit dice;
- extra 1d6 damage on surprise attack (+1d6/four levels;)
- climb sheer, normally unclimbable surfaces;
- naturally nimble fingers (manipulate small devices without training;)
- clever enough to decipher maps (and magic scrolls at 10th level;)
- bonus = hit dice to Change Situation, Avoid Accident, or Avoid Danger rolls because of sharp senses, nimbleness, and cleverness.