Buckle up, because this is going to be a long read.
I've been sitting around for a while looking through past chapters trying to figure out just how johns ability works, at least roughly. We can't figure out his ability level because his only static stat is trick at 10, all is other stats fluctuate greatly depending on who's abilities he copies. So the level equation is useless. not to mention the fact that we have no idea how it even works. We have no way of measuring "Mastery" or "Potential", nor do we have any number to go off of, but I digress. We also can't figure out how long he is able to use an ability he copies. We can take guesses, but its hard to tell just how long assuming its on a timer and not some other factor like memory. Though its likely not that either.
What we do know is this:
1. John has the ability to copy other abilities by seeing someone use it.
2. John can see aura's, basically the energy it takes to use an ability.
3. He does not need to have his ability active in order to copy it. (ch. 71, his ability was off up until he started healing Sera, Elaine's ability was off when he activated his.)
4. His stats change depending on who's ability he takes.
5. It seem to take some kind of conscious effort from john in order to copy an ability. He does not just see someone and automatically know it.
6. He is able to combine aspects of more than one ability in order to create unique moves,i.e. Blades of Wind using Whirlwind and Demon Claws.
Now the evidence for most of this is obvious. Its the conscious effort part that is the slightly more difficult, although its still not hard to notice. As is apparent in ch.112, His regeneration stat is only a 1, while Juni's is a two. Now I will get into johns confusing stats in a second, but recovery is one of the stats that is always as high as the person with the highest recovery. So it should have been 2 if he had copied Juni's ability, but it wasn't. So we can assume that he didn't take it. That or his stats are more confusing that I initially thought.
Now on to John's stats. So, johns stats are weird. The only static stat he has is trick and everything else changes. Because of this he also cant be put into the level equation to figure out what level he is. But one thing I noticed is that whenever he copies an ability, it is amplified by some small margin. What seem to be around 1.5-2.0 points. At first I thought it might be additive in some way, stacking on to some kind of base stats. So I spent a good amount of time trying to see if I could figure out his base stats. But it turns out that this is not always the case. For example when he copied both Ventus and Meili's abilities, his Defense was only increased to 3, both of their defense level. But in the case of Zeke in chapter 108, his defense and power are higher by about 2 points. Then it struck me, Maybe john is just better at using Zeke's ability than he is. Think about it, Johns ability is all about taking other abilities, so if he gets good at all of the general types of abilities (Physical enhancement, increased movement speed, etc.) Then he might just know a better way of manipulating his ability. Maybe using the defensive form on his fist and using that to land a harder punch when Zeke can't even use both form at once. Something like that. I mention this concept a little more in the last paragraph if you wan't to see me talk about it further, but for now i'm going to continue with john.
If it is not what was stated above, then he probably has some low base stats that abilities are added on to. This is going to be mostly assumptions as I'm going to be using the level equation, or at least the way it is understood on the wiki. Using the Level equation, we can use his original level of 1.2 in order to figure out just how many points he has. Basically, it is Level equal to the total added stat points(P) times the level of mastery(M, being either 1 or 2) all divided by 10. Using this, he should have a total of 12, meaning that he could have some reasonable stats. If you put it into a calculator with an extra 5 due to his max trick, he would actually end up a 3.4 without copying any abilities, which is pretty good. But this stuff is not very applicable given that is seems that stats don't really have much to do with "Potential" or "Mastery". They seem to be completely independent variable on there own. Blyke can increase his speed by using the thrust of his lasers in order to move faster. Potential and Mastery affect the stats, not the other way around. Mastery also has way more influence than potential, which makes sense, but I digress.
Now, how john actually copies an ability seems pretty straight forward. As far as I can tell, he NEEDS to see the ability in an active state in order to copy it. He does not need to have his ability active to copy it, he just needs to see it. Now one thing that come's to mind is weather or not he needs to see the person or the ability itself. For Example, he sees Arlo's Barrier but not Arlo, can he copy it? Given that he can see aura's, and as far as I can tell no one else can, I get the impression that his ability to copy is linked to the aura in some way. Sort of like how Remi can see things like electrical currents even when her ability is off, and when its on she can control electricity. So maybe johns is similar in that he can sense aura's and such, But when his powers are on he can control it in some way, weather it be his own or someone else's. Because of this, what I propose is that the aura is possibly the "DNA" of an ability. He reads the information and copies it using his own energy/aura. I'm likely not the first person to propose this idea, but its not like I'm looking.
So the only thing left are Johns actual level. As previously stated, its impossible to find out johns level with his stats the way they are, so its really just a guessing game based on gut feeling. He's at bare minimum a 6 because he beat Arlo. Stat wise, he could easily become a 10 if he finds the right people. But, his mastery and potential are absurdly high given how much versatility his ability has and his general mastery over it. He has to rank very high. If I where to guess, probably around Seraphina level if not higher. Keep in mind that he is proficient in all the common types of abilities, but likely not in all the rare ones given how few of them there are. You can find 100 guys who can run fast, but its not often that you find one that can stop time. So he would probably lose to Seraphina in a 1v1, but give him some time and he might be able to beat her. Though I am unsure of this given that he has been proficient in every ability he has copied up to this point, including things like Barrier and Whirlwind.
That's all I have in terms of info on john's ability. This is all of it compiled into one area. I hope this is some nice food for though. Tell me if I missed something or if you have an idea of your own. If there's anything I know, it's that a group of people trying to figure out something is much better then just one person. Some of you likely saw some details that I didn't and I would love to know about them. If we put out heads together, we can probably get very close to figuring out how john's ability works. Thanks for reading!!
This is in reference to the 3rd paragraph on how ability mastery could be more than just use in combat. Mostly this is on a different type of growth and and growth of an ability in general. Lets use Seraphina as an example. Tell me, how hard it is to master the ability to stop time in combat? The answer in not hard. You freeze everyone and hit them all while they are frozen in space. It may have taken some time to figure out things like rewind and such, But the result is the same. You move extremely fast, hit extremely hard, and can take down groups in an instant with out really giving it much through. Its like Saitama, all tactics fall in the face of absolute power. So what else is there to master? Given that she was able to beat her mom with basically the same ability, there is probably something more than just application in combat. For example, freezing everything but one small spot, being able to have the freeze spread faster than it initially could. There could be more to using a power than just how its used in combat, kind of like manipulating the energy to make it more effective, Make your skin harder, make you run faster, etc. If I where to guess, this would probably be why john is so good at controlling all abilities he runs into. Odds are a lot of them just feel the same just with a different effect. All the increased movement ones feel similar, same goes for the defensive ones, ones that make you hit harder, so on and so forth. If this is not the case then she just had very little room for growth. John on the other hand had an enormous amount of room to grow. Like I said, mastery has a much larger influence over the level equation than anything else, as it moved him from a 1.2 to at least a god tier within the span of a year or so assuming he got picked up by Claire in high school. He may have taken the time to master all the different types of ability in order to never be taken by surprise. So he might just have a better feel for these abilities and how they work. As well as how energy works in general. He might know how to better use it or apply it to make it more effective. But this is just a hypotheses.