Yea I think this is a very interesting, and cool, alternative to just adding new classes. The problem with WoW is that it’s such a commitment to reroll an entirely new class, it would be cool if the talent trees could shake up the existing classes a bit more and expanding to 4th, or even 5th talent trees could make things interesting!
I’m not going to get too in depth here, this is an off the cuff post to lean into the idea but I’m not doing a fully reviewed balance pass to make sure it fits in. This is just the concept.
With that said, I really like WW Monk in retail. More-so the concept of a lightly armored, highly mobile spiritual fighter wielding a staff. I think this would fit in very well as a Rogue tree. I’m also not great at coming up with names so I’m going to just describe the talents 
11 point talent - Grants the ability to equip staves but you can no longer equip any other melee weapon. All melee abilities will use the staff unless expressly stated otherwise (ie, requires daggers). You can no longer use Stealth. Staves cannot be poisoned.
21 point talent (p1) - Sprint’s cooldown and duration is reduced by 50% and but now has two charges.
21 point talent (p2) - A crippling strike that causes the target to become slowed for 10s. Requires staves and costs 70 energy. Generates two combo points.
31 point talent - Repeatedly strike the target with your staff, causing damage to the target every second for 6 seconds (channeled ability). Each strike applies a 1s stun that does not share diminishing returns with other stun effects. Costs 90 energy, 5 combo points, and has a 60s cooldown. Requires staves.
Anyway, the core idea here is that I’m trying to lean into that monk play style. I think it should de-emphasize crit and focus more on raw attack power, possibly making strength a more desirable stat for this build.
I think more would need to be added to offset the loss of both stealth and poisons when pursuing this build, but like I said, I just wanna throw down a quick concept and not a completely refined tree 