One thing that has always bothered me about 2e thieves was a breakdown between the iconic D&D THIEF SKILLS and certain non-weapon proficiencies. I still think of ventriloquism and disguise as alternate thief skills, yet they have a different mechanic to determine success from climb walls or read languages. Odd.
I could, as a 1st level thief, have a 60% chance of creating a good disguise (assuming a 13 charisma), but less then 35% in doing most of the canonical thief skills, except climb walls.
One way to resolve it is to make several non-weapon proficiencies into thief skills. I like this approach in part because some of the non-weapon proficiencies had been used a theives' skills in previous editions. I also like it because it gives a thief more options. I can see an urban thief as quite different than and adventuring, dungeon-crawling thief. I could see both as quite different from a yazuka and assassin. You could start with a list of twelve skills starting with 1 point and 16 points to build with no more than 6 points going to one skill.
However, once you make the thief skills and non-weapon proficiencies the same mechanic, it makes more sense for all the thief skills to become non-weapon proficiencies. This allows characters to have a narrow band of skills with better than a one in three chance of doing anything. This also ties into the kits idea, but that will come later in another post.
To preview a bit where all of this is going: Warriors will be differentiated by weapon proficiencies and specializations. Rogues will be differentiated by non-weapon proficiencies. Wizards will be differentiated by schools of magic. Priests will be differentiated by domains. Psionicists will be differentiated by disciplines. Certain non-weapon proficiencies can add flavor to any character, but I want to get rid of certain silliness in the various Handbooks. (An amazon kit for every class. Ugh.)
Back to the topic. To re-skin the thief skills into non-weapon proficiencies:
Pick Pockets: DEX +0
Open Locks: DEX -1
Find/Remove Traps: WIS -2
Move Silently: DEX -1
Hide in Shadows: WIS -2
Detect Noise: WIS
Climb Walls: DEX +2
Read Languages: INT - 3
Next up, more on the kits.