I'm currently writing a game that is very much inspired by Chinese cultivation fiction (leaning towards Xianxia not Wuxia). Its using the Cortex Prime system. It won't be out until the Cortex Creators Studio is released, which is still being developed as well.
Here's the Cultivation mechanic I've developed for it:
I've simplified the cultivation realms for the sake of gameplay...and it is very much build on the Cortex Prime ruleset... https://www.cortexrpg.com
Characters of higher tiers are significant threats to lower tiers and within the tiers there are general any number of levels (most authors have their own versions of these). The goal with this is to represent a large advantage to the higher tiers while also giving advantages to the individual levels within each tier.
In addition, Cultivation power is also something that can be sensed by other characters, so I've implemented a way of suppressing your true Cultivation scale as well, allow you to power down to a lower tier if you wish. While powered down, other characters with the ability to sense your power will sense your powered down tier, however, you are also mechanically at that tier until you quit suppressing your power.
Cultivation Tiers/Levels
My take on the tiers is a simplified version of what is typically used in the fiction. The names and descriptions are also simplified for the ease of presentation.
Tiers
The above tiers are used to determine your Scale. Foundation Formation is has a scale of 2 Tiers over Mortals. Nascent Soul has a scale of 3 over Qi Condensation.
0 Mortal (Mortals always roll a d4 if they use Cultivation)
1 Qi Condensation (learning to harness the powers of Qi)
2 Foundation Formation (Building the foundation of Immortality with Qi)
3 Core Formation (Forming your Qi Core)
4 Nascent Soul (Birth of you Immortal Soul)
5 Immortal (Maturation of your Immortality)
Levels
Each of the above Tiers are broken up into 4 Levels that represent the character's power within the tier. I've simplified these levels for the benefit of game mechanics as well.
Early Stage - d6
Mid Stage - d8
Late Stage - d10
Peak Stage - d12
Trait
A character's Cultivation Trait is listed as the "Tier Name Level Die". A Foundation Formation stage character at the Mid Stage would be listed as Foundation Formation d8.
Using Cultivation
When using your cultivation you would compare you would add your Level die to the the pool. If your Tier is higher than your opposition, you get to add your Level die a second time and you can keep and additional die from your roll for either your Result or Effect for each Tier you are above the opposition.
Example
We have two Disciples, Meng Hao and Chen Fan.
Meng Hao
Foundation Formation d8
Chen Fan
Qi Condensation d8
Both would add a d8 to their pool when using their Cultivation and choose 2 Die for their Result as normal.
If these two were to get into a fight, they would both get their d8, however, Meng Hao would get an additional d8 due to the 1 Tier difference between them and could either choose 1 extra die for his result OR 1 extra effect die from the roll.
Lets add another example.
Master Li
Nascent Soul d10
Master Li comes across the above fight and decides to stop he and enters the conflict. He would add his Level, d10 to his pool against both Disciples. Against Meng Hao, he would get an additional 2d10 to his pool, and could get 2 extra dice for his Result OR Effect (in any combination). Against, Chen Fan it would be an extra 3d10 to his pool and 3 Extra Result/Effect dice.
The above is the early draft of a scale mod I created for Cortex Prime to model Cultivation levels for my game.