Since Wesker is like pissed off since he couldn't create his perfect world, his spirit has been lingering around the world. So these demons come and offer him to resurrect for some unknown reason, because demons are like that and all, I don't know we'll retcon it later. Anyways, the catch is that he won't be able to go back into his old body since a dead body is a ... I don't know... a dead body? So he'll have to resurrect as something that was close enough. So get this, he resurrects as sunglasses since when people think of Wesker, they think of his sunglasses and the sunglasses might as well have been an extension of his body.
So the thing is, he isn't that intimidating as sunglasses, but get this. Whoever wears the sunglasses will be possessed by Wesker. It'll make such a interesting plot since the protagonist will have no clue about Wesker's new form and yet there'll be a lot of mystery as why so many people are trying to destroy the world since Sunglasses Wesker is going to be possessing a lot of people. The only clue they'll have is that the only thing these people have in common, is that they wear sunglasses. Thus Chris will start to have nightmares about Wesker and eventually we'll have a detective plot with the finale being the true final fight of Chris vs a pair of floating sunglasses!
Imagine, explosions in the backround, Chris is half naked (for some reason) completely baffled and filled with emotions that Wesker is alive (and that he's fighting a pair of floating sunglasses, they started floating now? Yeah sure! because the power of... revenge! I don't know, we'll retcon it later).
The floating sunglasses gloat, "I'm unimpressed Chris. It took you this long to finally figure it out."
Chris with his usual... something face responses "Wesker. I thought you were dead. But deep down inside, I knew that was too good to be true."
Then starts the long conversation with Chris having a QTE fist fight with floating glasses Wesker. Becarful though! Floating Sunglasses Wesker can shoot revenge lasers out of his lens!
Edit: Oh also, Wesker has a instant kill move where he tries to float into Chris' eyes making him wear himself so we'll have a QTE with chris trying to pull away the glasses before Wesker can fully possess him. It'll look so epic. --- "Nma... Tsua... Choji...!" - Inohara Masato (Looking back on his life)
The possessed glasses of Wesker? Hmm... Jake Muller is immune to it, so he can wear all the time... except if someone stole it from him then he/she will be possessed by Wesker. --- "Get up!! Show me your true power!" Ryu's victory in SF3