What limits can I add?
I'm creating an OC who can create a personal version of anything. To be more precise, he replicates anything he wants, and this "replica" is linked to his soul and even partially changes characteristics (usually only physically, but if it's a powerful object or a superpower itself, it changes its powers and/or power source) to match his personality or fighting style (for example, if it's a weapon, it can change model or type; for instance, a pistol can transform into a revolver because it suits his fighting style better, and if it were something like pants, it would be comfortable and in his style, as well as being custom-made). These replicas "develop" and "improve" with use, and I admit it's very overpowered, but it's the only way my character can acquire what he needs to complete his mission without having to constantly change artifact after artifact. The same goes for anything else, and it's better that these replicas keep improving and changing in appearance and power.
To limit it, I created certain rules, but I don't think they're enough, so I'm asking for support. They are as follows:
°I can only replicate someone else's power if I defeat them.
°With artifacts, it's enough to steal/buy them from the owner(s).
°For artifacts without an owner (like an ancient artifact somewhere in the sea or something like that), I have to have them in my possession to create the "replica."
°A "replica" of a power won't transform into an artifact and vice versa unless an external factor intervenes (like weapon assimilation and similar).
°If I replicate something metaphysical (like economic status, a doctorate, a job), its "improvement" doesn't necessarily activate with its use; sometimes it requires doing something related to it (for example, if it were a doctorate, it's not enough to just use it to gain access to related places or positions; I would have to publish "real" research).
For now, these are the rules, but I think it needs more to make it feasible as a strong power, but not too powerful.