You can use it if your players don't mind it. That said...
TRPG had always been following the "Hollywood Movie Laws" to certain extents, ie. The main character can be shot and blown up a hundred times, but they would come back next scene and fight twice as hard.
I mean, the "fast healing priest" idea probably started from Dungeons & Dragons, just to give players excuses for doing so while maintaining that heroic aspect.
In a game of CoC, the idea is you either solve the problem at hand or die trying. It is a lot easier to die there, but that's part of the design. A "crippling function" there is mostly mental-related due to the horror factor. Guess it could be reasonable to add a physically crippling function there.
But...
The flow of the scenario?
I mean, a scenario is usually an ascending curve of difficulty, with a time limit of days.
A PC don't usually have a day off for sleeping in the hospital, while the world around them is turning into space-color.
And if they have gradually-increasing aliments that they don't have the time or resources to treat, that becomes a descending curve of capability.
That's kinda why even in CoC, where this kinda thing can on paper work, you still don't see them. (Mental conditions might get your PCs weird at certain times, but by-and-large its not a generally-limiting thing and they can still do 99% of what they did. And for the PCs that have gone that far down, they're probably ready for their one-final-exit-scene anyhow.)
Ascending curve of difficulty vs Descending curve of capability... If the players are real unlucky, you can have a bunch of people who must fight the final evil all in mobile-wheelchairs just because of bad luck.
...That ain't usually that heroic. (Unless it's a Bubba Ho-Tep situation where all your PCs live in old-folks home... Hmm, that could work...)
And for many players, non-heroic = non-furfilling. Even CoC is about heroism, its just their heroics are defined differently from DnD-types.
And some people do prefer that, so, like I said You can use it if your players don't mind it.
It's just the reason why stacking wounds have always came up, but so few games use them and mostly only for optional rules.
(Come to think of it, the one genre of games that commonly use debilitating negative stacks... Japanese ryona hentai doujin PC-games with female protagonists? !!!!!=_____= )
