@mourgos Good thinking! Certainly a thing to consider.
I think @Takiro is right though. Otherwise no sites with user content would be possible unless they verify each upload, which is just can’t be done since there isn’t a registry of copyrighted works.
Unfortunately this is pretty much what legislators are pushing to more and more. YouTube already does it to some extend with mixed results. Other major websites will be forced to implement filters, too.
But it’s getting pretty off topic.
It really depends on your strokes, I think your camera quality is also portraying the markers differently than they are in real life.
If I grab a random image from the interwebz, you’ll see that the marker strokes also get darker with successive strokes. In your photo, they appear to be completely uniform from the get go. That’s what I like about Copic markers, you can create gradients with only one marker. The effect gets stronger if you use multiple, but you don’t need to!
In response to @RamonM:
@Takiro, @tachiko and I were discussing the realistic markers, whereas @darkhog wanted people to test theirs. So somehow the thread got hijacked towards a discussion of realistic markers…
I used the foam tip of my Ciaos for this, they make pretty uniform colors, and I did it petty slow. The blue patch in the second row is made with the hard square marker tip, it shows the effect you describe a bit better. The paper used does also affect the look a lot.
From my experience they don’t really get much darker with successive strokes but become a lot lighter with fast ones, in the end, making gradients is a combination of both. For really good gradients I use the colorless blender, I could make a video showing how that works if that helps anyone. However that is different with some colors, I don’t know exactly why that is, same reason why some colors don’t mix properly I guess.
While that is true, I think it’s still important that when you call your brush alcohol markers they should work at least a little bit like them. checking out the real thing for adjusting is still a good idea even when perfect replication is not the goal (and in my opinion not even desirable in most cases).
Since I have Copics at home, I thought it’s a good idea to compare it and tell about the difference so the preset can be tweaked.
There is also the “dry copic”, not an actual marker but just an old pen. Fresh Copics apply a lot of color, making it look like on my photo with my rarely used Copics. But I still have some older ones specifically put aside because they’re almost dry, don’t apply much color to the paper and make it easier to work light and make some effects, that could be it’s own brush preset, and with them you have to paint over the strokes a lot more to make them even and darker.
I have a whole stack of regular Copics mixed in with a few brush tip variants next to my monitor. I tend to use them quite quickly, so then it’s possible to build up value. I always try not to soak the paper too much, because that makes blending and later passes more difficult.
It’s a good idea to have worn markers as well.
There are various types of alcohol markers from what I see @Takiro has flat nibbed ones there are round tip ones too. With the round tip ones one can easily blend colours by layering from light to dark. here is a video of one person colouring with the round tips for reference
With that said, I agree with @Takiro the brushes in the bundle are a bit week for markers, they have softness to them. may be texture and blend mode can be adjusted.
I have updated the preset according to the feedback, Please redownload bundle from the OP and tell me what you think. Also if someone could make the icons for the brushes that fit with the other Krita icons I’d be very happy.
These are mine
The round tip is a soft foam, emulating a classic paint brush, hard to get used to but if mastered everything you need. The square one is a hard tip.
I have mimicked the hard rectangular nib in my brush pack. So if you change the tilt direction of the pen relative to the tablet surface, you’ll get a wider contact area like you get from the real hard nibs. If you touch it with the pen held straight down, it’s like the pen nib that’s on the end of the regular marker. It might be nice to mimick the brush version too (and worn ones for both).
In principle, everything is available for this in Krita, including a modular system for brush icons. You can also use @TheTwo’s template for this, or create one yourself. I have created several personalized templates for my own use, but an icon with my nickname in the image might not help you. 
If you click on “Load from Icon Library” you can click-build your Icon
And as you can see in this screenshot, you can also add own icons to those Krita has on its own/is shipped with.
Link to the template from @TheTwo →
Michelist
I would like for someone to test the current, updated preset against real copics before finalizing the brush and submitting the final one with proper icons.
These three strips of my webcomic, The Secret Report, were made using this brush (aside of the lineart and frames/bubbles):
Please someone test the updated version of the brush against real copics so I can finalize it.
Please someone test the current version of the brush against real copics. Did some improvements. Also, remember to use the brush tips as the brushes are designed to mimic that one specifically.
I would, if I had real copics.
Michelist
I too would test if I had access to the real ones, but I don’t. 
Well, @Takiro apparently has access.
