"Western fantasy" (or the Easts interpretation of western) and cultivation novels generally have some aspects similar to each other.
They both have common ground in "individuals with power" and "skill progression."
How I will define western fantasy;
it should in include mythic or magical creatures (includes "Demi-humans and most monsters like goblins)
magic as a ubiquitous force or as a "mentally generated" energy (like through meditation)
a system of "jobs" which can be visible(via stat plate example is THE DEATH MAGE WHO DOESN'T WANT A FOURTH TIME) or invisible (I don't remember any good examples from the top of my head, but they exist,)
religion/gods is usually included in this style of fantasy
magic items (most often includes potions, armor, and magic crystals.)
Generally the system of government is mostly kingdoms/empires (oligarchy being left out is a sad boy right there.) democracy is usually excluded due to it not being of the medieval time period (for the most part)
Most power is very specific, and what I mean is think elemental mages; light, dark, fire, ice, wind, and earth (traditionally anyway.) sometimes they don't use the same type mana. Think of magic the gathering, so you have colored mana in the specific elements. Then you might have "wizards" that can use colorless mana, so they invoke different elements (let's call it "pure mana.")
Or other powers that are specialized is warrior energies like "ki" (even tho that is taken more eastern fantasy you still find it in western due to it being a good concept, and that it helps balance the playing field for warriors because wizards and mages be op as hell,) and faith based powers.
While cultivation is more how should I put this. It's powers are more connected, and this is mostly due to the concept of the "great dao" (im not to familiar with what it actually is/means due to most cultivation novels being over 3000 chapters long or being never ending which is unique perk that cultivation novels have ill talk more about this later.) I understand it as rules/laws that govern the world that give individuals power (roast me in the comments if you have a better idea of how to describe it.)
The cultivation powers are usually broken down into good, evil, alchemy, and body cultivation (evil is usually forbidden cultivation or demonic cultivation.) (body cultivation is bodybuilding on ultra steroids.) (you don't need me to explain the alchemy one if you read cultivation novels.)
Then you get into the "laws" section of cultivation usually fundamental rules of the world like fire, ice, or lightning.
The powers are very talent based (you don't have power or talent no respect for you my good sir! Except when you are an alchemist.)
The energy that the cultivators use is for "techniques." These are weapon and movement arts. (moments arts are like flash step or flying) sometimes you have defensive arts too but less common.
(If you need a good reference, for what I'm talking about In this part look into Unrivaled Medicine God it has many of the ideas explained above)
They also have a unique system in these type novels "worlds/pocket spaces." They are generally hierarchical high order world to low order worlds. (again look to unrivaled medicine god for how this works.)
Another unique aspect of cultivation is the breakthroughs. Most often the lower level breakthroughs are nothing to mention, and they happen at specific energy capacities most of the time. This is not the case once you get higher though. How you may ask well it's when they have to go through tribulations or trials when starts to diversify from normal fantasy. When going through these "tribulations" often enough it changes the very energy they use. This often described as a qualitative change.
The reason this is a unique thing to cultivation is due to how the power system of magic in fantasy works. Most often in western fantasy magic doesn't really change maybe you get an additional affinity, but most often it is only cares about the quantity. (While yes they do often talk about purity of mana, but that is just removing flaws that doesn't quite cause a qualitative change to occur.)
(I know I just made half the people that will ever read this either bored or angry about explaining all of this, but it needs to be explained.)
(This section will start talking about combining them don't worry)
Section A
First I would like to put forth an example of what I think we should aim for.
I think Warlock of the Magus World fits the bill on combining the two genres. (BEWARE AFTER THIS POINT THERE WILL BE SPOILER FOR THE NOVEL skip to section B if you want to avoid spoiler I do recommend you read the warlock of the magus world if you haven't already) It uses magic but at Points in the journey he has to make a "breakthrough" using materials to have qualitative changes while gaining quantity increases in magic. The main character has to find or make new spells that use this energy. Then it loops back, but with a wider area to explore that was limiting him before.
I'll skip some of the plot to shorten the amount of reading.
The very power he gains is derived from the world/pocket space very much like the great dao I talked about earlier. Then when he reaches a certain level he learns that the very planet is also somewhat a cultivator as well.
The power levels go from 1 to 9 at nine you gain immortality at this point nothing can stop you.
How you get to eight is you combine laws (in this case they act more like attributes.) this combination of law must be able to use the law of time, and when you learn the law of time you become a level nine being
the main character originally stole the law of gluttony (but change it into devouring) he used this to steal the other sins, and after he had them all he combined them into what is called the "Original sin." The reason he is able to learn time law from this is due to all intellectual beings being able to sin regardless of time.
Section B
To marry the two genres to make an aberration like western cultivation is an interesting prospect that needs skills I just don't currently have.
You need to balance the energy quantity then have a boundary that will qualitatively change the energy into a higher form.
Then you have to figure out how you will deal with laws are they just fundamental rules, or is it the broken down form of a primordial energy?
How will you deal with the pocket space or worlds?
End section
Mind you this whole chapter can be takin as a grain of salt, but it does have good points on the fusion of the two topics. This was a good mental exercise for myself. This is not a common topic as far as I know, so I thought I might bring this idea to the table.
Also thanks to anyone that actually made it to the end section. I know I'm horrible at making it not boring to read but I did love writing about this topic myself.
You have full right to blast me in the comments if anything is wrong, boring, and misguided.
From a terrible writer have fun.