Should I tinker with Thief skills again?

Thieves. I love them. Love to play them, love to have players play them. It's the whole 'brains over brawn' thing that makes me enjoy them.

But, like many people, I sometimes get annoyed at how they've been presented, and how their skills work. Usually I don't mind the percentage based skills, but the chances of success are pretty low to start. But I've always considered other ways to do it.

In Flying Swordsmen, I copied how they were done in Dragon Fist, which is mostly how they were done in 2E except converted to a d20 roll instead of a percent. The bonuses I gave to the skills were to represent the basic percent chances of a starting thief, and players were allowed to distribute bonuses to the skills when they leveled up like in 2E. That works fairly well, but does lead to some confusion (like the +13 to Climb Sheer Surfaces being thought of as a typo since other starting bonuses are low single digits).

In Chanbara, I use the Ninpo system which is based on 2d6 rolls similar to the Cleric's turn undead chances. I thought it was pretty clever when I came up with it, giving fairly reliable odds of success due to the bell curve, but in practice having to decide the TN for the roll for each situation slows things down at the table unless I've anticipated ninpo being used and included TNs in my adventure notes.

In Treasures, Serpents and Ruins (TSR) I'm currently using the classic d% skills, but using the most favorable progressions.

In TSR-East, however, the ninja was based on the Halfling class in BX/BECMI, so it has hiding 1-9/d10 outdoors, hiding 1-3/d6 indoors (slight variation on the Halfling's 1-2/d6 indoors), 1-3/d6 to move silently (1-2/d6 if wearing brigandine or heavier armor). I also gave them detect traps 1-3/d6 (but not remove traps), detect secret doors/sliding passages 1-2/d6, and hear faint noises 1-2/d6.

The yakuza class can locate traps 1-4/d6 and disarm them 1-2/d6. Also, depending on which mystical yakuza tattoos they select, they could also possibly: detect secret doors 1-3/d6, hide/move silently 1-3/d6, hear noise 1-3/d6, escape shackles or bonds 1-2/d6, climb sheer surfaces 1-9/d10.

Jeff is playing a yakuza in West Marches just to try it out, and it's been going pretty well. He took the spider tattoo so he can climb sheer surfaces, and he's been using it to good advantage. But he's only level 3 so I don't know if dissatisfaction will come into play at higher levels when the scores don't improve.

So now I'm wondering if I should edit my TSR-West rules (the standard D&D classes) to match the x/d6 or x/d10 demi-human class abilities. TSR-East characters start better, but don't improve on their chances as they level, just as demi-humans in BX/BECMI. The whole point of the Thief class is to get that delayed gratification (like with the Magic-User) of surviving to high levels when your skills become more reliable.

So I've got four choices:
1. Leave things as they are and just let the Thief (and subclasses) continue to use d% skills.
2. Flatten the curve, so thieves use d% but start with higher chances but improve more slowly
3. Go with flat x/d6 or x/d10 chances for the character's whole career
4. Go with x/d6 or x/d10 chances that improve at certain stages in the character's career (like when attack bonus and saves improve)