Red Set wouldn't be too powerful or too weak
Make it advance along the character! Same gear, rising abilities and emergence of some cool powers that might fit the character. We are talking about a lot of objects with magical nature having a synergetic effect. It could as well be not understood by mages, considering the effort to make one and research.
There is something like that in Earthdawn RPG. It's called Soul Weaving if memory serves. The more you uncover about yourself and history of the object the souls of both (in Earthdawn literally everything has a soul, think of the Force from Star Wars) get in sync more and more. That rusty old dagger you got from your grandfather… it's just a knife, but for you its a memento. That's sync level 1. Maybe it cuts rope better or something.
During adventuring some dwarf recalls that you look like its previous wielder, remembers the moment when adventurers grandfather saved him from slavers. He explains to you more about its past and about the island where you met. Adventure or two later, they might find their way there and discover… more feats that involved this dagger. Maybe more people who freed by it, or a slaver with a nasty scar instantly feeling hatred for the wielder, despite not really recognizing the dagger itself. Etc etc. You can get at about as high as you want. One of my players actually passed his literal mantle on his son, telling him that people will remember the human in the green cloak. His son now will be recovering the past of his father by means of legend that he left, his mark on the world.
Damn, now I want to play me some Earthdawn again!