TBH within the context of a hero I am not entirely sure of whether this quirk is overpowered. Partly because there are no clear limits to what the quirk can or can't do. So far its limitations are... momo's knowledge and her fat levels. The quirk also limits momo is that it provides no physical augmentations whatsoever, thus her physical capacity can only be that of a normal human within BNHAverse. Momo is also severely limited by the law. If she starts fighting crime by making gold gadgets then she is bound to crash the world's economy. Overall even in the best case scenario for momo to abuse her quirk to its fullest she needs technical expertise so as to make sufficiently useful and powerful things out of it. So far she has made some useful stuff but making ropes and tape is pretty basic in a world where children are able to make midoriya's gadgets. Pretty sure guns wouldn't really be allowed for her. Momo would actually be better off if she left the hero course and joined the support department, where she'd get the technical expertise to fully abuse her quirk on the field.You’re completely right on creation and that’s why I chose it too. Creation is one of the best quirks in the manga. So much so that Horikoshi gave it to Momo because he thought it was an overpowered ability and would be more interesting on an inexperienced character rather than a pro hero.
It’s such an underrated quirk because it’s not as flashy as the others and Momo uses it in the most boring ways.
Now, in this scenario it works mostly because you wouldn't be bound by morals or ethics and you have other tools to fully abuse it. And even then, the stuff outside rewind, overhaul, dupli arm and flight is almost unnecessary considering the sheer extent to which you can manipulate matter at will at that point. Though it is fair to say that advanced scientific knowledge would really further how insane the combination is.