Richie can replace anybody in any band. He is brilliant beyond belief. I'm pretty sure he could replace Steve Vai in Steve Vai's solo band.
I don't think it will happen or I want it to happen, but Richie is the man for the job. However, tbh, I don't think anyone in Maiden is replaceable - this lineup is magical and will forever be the best one.There are two guitarists that could easily replace the aging guitarists in Maiden : Roy Z and Richie Faulkner.