First, I think that if you cannot come up with a valid reason to include the system it is not needed, and I don't even read stat sheets a lot of the time (simply because they don't add anything). That being said, I know people love their LitRPG's with stat boxes, but I would personally appreciate it if the system is actually an integral part of the story.
HP, Stamina, Magika, etc. Those things are only really needed if it is a game type world. Honestly, I would probably drop the whole LitRPG idea as whole, unless you are good at math. Or you don't mind creating a large inconsistency, as they often do. You want a goal for the MC? Just drop in a world ending type of plot line. But how do I make this plotline LitRPG (if you are deadset on it)?
The system is being destroyed by Eldritch creatures eating the basic building blocks of your world. They are even eating people's stat boxes! The numbers are jumbled, and nothing makes sense. People are getting corrupted by the void, and even the native monsters are becoming warped.
I actually really like the idea of a LitRPG system existing in a world as a support put in place by the godly ascended figures in a Cultivation world. Basically, it used to be a Cultivation world, but it turned into a LitRPG world because some ascendeds decided to create the system in order to help those lower than themselves cultivate faster and with less effort.
I have actually been working on a system for a world in which the characters who create the system are originally transmigrates from Earth from thousands of years ago world time, which translates to only a small handful of years Earth time due to time flow differences.
I really like the concept, but I've been stuck for quite a while on the implementation of the system itself. Tried to start writing that story once and my brain just crashed as soon as I started thinking of the implications of the system I was using at that time, and I wound up scrapping my rough-draft and went back to the drawing board, and then put the thing on the back-burner where it's stayed till this day.
All that aside, the origin of this idea was actually the fact that I find myself interested in the stats sheets a whole lot more in Cultivation world novels that just happen to measure the physical stats as a form of bench-mark. Like, the stats aren't just numbers. The person's gaining power due to their cultivation, and then they use some kind of objective measure of comparison to gauge and put numbers to the person's strength, agility, and toughness or something. (That's another thing about the cultivation world stats. There are always a much smaller number of them too.)
It just seems like they tend to keep it a lot more reasonable both in terms of not letting the numbers get out of hand, and also giving the numbers actual relevance, so the cultivation world stats are always a lot more interesting than LitRPG stats.
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power systems are rather unique to the person and it has helped a ton come up with ideas XD.
Seeing this comment triggered something in my mind, and now I'm going to go off fan-boying on Worm again. But, the main reason I have become such a fan-boy on Worm since reading it is because I am deep into the art of writing and story-telling, and Worm is the one series I'm aware of that just seems to do everything you can possibly want right. (Except maybe for softening the blow for sensitive readers. It most certainly does not do that. It does the exact opposite wherever it can.)
Anyway, Worm is something that has opened my eyes quite a bit on power systems. I especially appreciate how the power system in worm places a HUGE emphasis on forcing the characters to be creative with what they have rather than them just constantly getting stronger. What's more, you come to understand just how much more powerful it is to have a sensory ability Vs. a damage-dealing ability.
Near the end of Worm, everyone starts calling Taylor, the MC of the series, "the strategist." This is because her power to control bugs is really not that powerful a damage-dealing ability at all. It is completely unconventional in every way. However, what turns out to be the single most effective part of her ability is that she shares the senses of every single one of her bugs, and this helps her to coordinate others and guide them. Or, it can also allow her to go in with raw melee abilities and know where everything is without even needing to look with her eyes.
She stats out feeling like one of the least powerful people on the field, but by the series end, without her having gotten a single power-up other than a few range boosts, she comes out looking like the single most OP character out there just because she found her niche of commanding and coordinating.
From a writing perspective, this is very inspiring because it really shows you the value of placing hard limits on your characters and allowing them to grow in effectiveness without actually increasing their power. Even if you don't use anything that even looks remotely similar to Worm's power system, it can help you a lot in what you look at when considering the power system if you are exposed to works like this that place such hard limits on it's characters.