I'm sure it's been done before, I've never tried to raise guineas with anything but guineas....so Idk.
As far as Reeves and Silvers together as long as they are all males and no females around, you maybe could get away with it.
My personal experience with Reeves pheasants is that they are extremely aggressive.
You can not raise Reeves chicks with other species of pheasant chicks, the Reeves chicks will peck any chick to death, that's not a Reeves. I also absolutely have to have a barrier between a pen of Reeves and any other pheasants or they will fight constantly between the wire. These have been my experiences, yours may and probably will differ. Every pheasant has it's own personality, just like humans....some get along well together, some not so much! HTH