OD&D LBB Only Thief

 Since I recreated the outdoor survival maps in CC3+, I haven't actually used them myself yet. I haven't really been gaming at all unfortunately. But I have been slowly working on a system to combine the OD&D 3lbbs and Chainmail.

While doing this, I've been thinking about including the thief class. While I know the thief isn't traditional in a 3lbb only game, I feel it is a stronger fantasy archetype than the cleric is. So as I start working out this system for my future OD&D & Chainmail West Marches style game, and a solo game for my wife, I've been analyzing how others have treated the thief in this context.

I've looked at a set of notes of how Gary Gygax apparently thought about including the thief before Greyhawk (I honestly have no idea how dubious this claim is), as well as the following these other resources/clones:

Delving Deeper

WB FMAG

S&W WB

Spellcraft & Swordplay

7VoZ

Greyharp v1

Greyharp v2

Torch & Sword

Sword & Spell 2e1p (3p doesn't have thieves

Gygax LBB Thief

Platemail

Supplement: Planet Eris

What I did was analyze how the thief gains Hit Dice, Fighting Capability (or grows as a fighter if a FC equivalent isn't available), the systems used for Thieves Skills, and how Backstab is handled in each of these resources. This is the result of my research. 

Edit: I want to  note there is a flaw in my method. In the systems I analyzed, I did not check them against OD&D itself, but how they relate to the other classes in their own system. I might go back and practice this same exercise but see how it stacks against the lbbs.

Document	Hit Dice	Fighting Capability	Thieves Skills	Backstab
Greyhawk	NA	Same as MU	d100 system with racial modifiers	+4 2x dmg
Delving Deeper	Worse than MU	Worse than MU	4-6 on 1d6	+4 2x dmg
WB FMAG	Same as Cleric	NA AC As Cleric	1d6 roll under per level. Starts at 2, 5 at 10th level	+2 2x dmg
S&W WB	Same as MU	NA AC As Cleric	1d20 roll under similar to d100	+4 2x dmg
Spellcraft & Swordplay	Between MU & Cleric	Betwen MU & Cleric. Essentially a level ahead of MU	2d6 + level & racial modifier >=11	+3 2x dmg (2d6 system)
7VoZ	Better than MU (No clerics)	NA AC Between MU & Fighter. No Cleric	1d6 roll under 4 OL, no other adjudication available	+9 through +31
Greyharp v1	NA (Uses copied from Greyhawk)	Similar to MU (Superhero instead of Wizard)	d100 system with racial modifiers	+4 2x dmg
Greyharp v2	NA (Uses copied from Greyhawk)	Similar to MU (I think the +/-2 are typos)	d100 system with racial modifiers	+4 2x dmg
Torch & Sword	As Cleric	NA AC As Cleric	d6 system	+x depending on level
Sword & Spell 2e1p (3p doesn't have thieves	Worse than MU	NA AC Same as Cleric	1d6 5+ +1 to roll every few levels	+4 2x dmg
Gygax LBB Thief	Same as MU	NA AC Same attack table as Cleric	d100 system	Mentioned, but no rules given
Platemail	All classes are the same	Better than MU (no clerics)	leveld6 system 6 is a success	NA
Supplement: Planet Eris	Same as MU	NA AC Same as Cleric	2d6 and 1d6 systems	+4 2x dmg

Note on my shorthand: NA means the information wasn't applicable. Typically this refers to the fact that they completely scraped the Fighting Capability chart. Sometimes it was that they had just copied the d4 HD from greyhawk. AC means Alternate Combat. Since most did not have a recreating of Fighting Capability, I instead compared how they leveled in the Alternative Combat system.

I've been surprised by some of the results. I understand the thief gaining HD similarly to a Magic-User, or a cleric, but some documents make them gain HD slower than Magic-Users? Sometimes their Fighting Capability is even worse than a Magic-User in Delving Deeper v5
Thieves skills ran the gamut from being essentially worthless at early levels (like D&D is traditionally), to having a decent chance at success.
There really was not much difference in how backstabs were handled. +4 to hit with double damage, and it increasing to triple and quadruple at certain levels was pretty standard. Spellcraft & Swordplay was only a bit different since it is a 2d6 system.

Now I'm trying to think of how I want to handle the thief. I plan to take the XP chart from Greyhawk. I think I will go with a HD that either matches the Magic-User, or is somewhere between that and the Cleric. I think I'd give the Thief a Fighting Capability either matching the Cleric, or in between the Cleric and MU. For Thieves skills, since I am planning on Chainmail and stuff, I think I'd prefer one of the d6 systems. Either ripping from Lamentations of the Flame Princess (which is what I've done in the past) or taking one of the 1d6 or 2d6 systems shown above. I prefer for the thief to be somewhat competent at early levels. They're already not great at combat, so I would rather them not die constantly because they're tasked to disarm traps with their minuscule chance to do so. For backstab, I think I'd have to go with something a bit different than what is shown since I'm thinking about troop and man-to-man combat. +4 is what too large of a bonus. Maybe an extra die on an attack in troop combat, gaining more than just 1 extra die as you level, and maybe the +2 or +3 for Man-to-Man. 

I'm curious, how would you handle a 3lbb only thief? What would you change if you planned to use chainmail combat rather than the alternative combat system? Did I miss any other clones or sources for an 3lbb style thief?

Edit Note 1(because I'm positive there will be more): I later on realized how much of a dumb-dumb I am in that I didn't even check if Supplement 1: Greyhawk included Fighting Capability. IT DOES. It matches the Magic-User, but the Thief matches the Cleric in Alternative Combat. Odd? I added it to the chart, but I need this note to humble me for the next time I think I'm smart. (rofl)