I agree with those who don't see Evolution as a long-term reunion. They're back together just long enough to put The Shield over before disbanding again. Pretending they were to hypothetically add a new member to the group, let's run through the list to see who would be the most viable candidate:
Cody Rhodes - In a way, he'd be perfect. He has the look, the age, youth factor, etc. on his side. What he doesn't have is an interesting personality, and just slapping on a suit on him and having him cut promos about how he's the future isn't gonna make up for his notable lack of charisma. On top of that, it'd be way too similar to his role in Legacy for my tastes. That group had the same exact characteristics to it as Evolution has, and I don't care to see a repeat of it with couple of the same members, seeing as how Orton and Rhodes would both be sharing screen-time as allies again.
Alexander Rusev - No. I like the idea of a female manager like Lana having to control and manage this huge behemoth of a man. Sticking a foreign heel like this one who speaks more with action than with words in a group like Evolution seems odd and boring.
Sheamus - No. His age isn't the issue since Batista was about the same age when he joined (although a younger guy wouldn't hurt), but unlike Batista and Orton when the original incarnation of Evolution began, Sheamus already has a long list of accolades to his name. Royal Rumble winner? Check. King Of The Ring winner? Check. WWE Champion? Check. World Heavyweight Champion? Check. Seems to me he's already built quite a resume for himself without the need to be seasoned by a group of veterans, so sticking him in Evolution wouldn't make much sense imo. They've already pushed the guy hard enough in an attempt to get the people to buy into him as "the future", no reason to continue doing so when it's clear the audience sees him more as an upper-midcard talent than a main eventer.
Big E - Maybe just me, but this could work. Big man who can work, talk on the mic (when he's allowed), has a cool signature mannerism (the Five-Count, though he's yet to utilize this on non-NXT WWE programming to my knowledge), etc. Explain why this wouldn't be a decent choice. It's not even like the guy has done anything special since splitting from AJ except carrying around a dead title that he hardly ever defends.
Ambrose/Rollins - I can see either of them working, especially Rollins. It'd be a great way to split The Shield apart and send Reigns off on his own, though Ambrose and/or Rollins spending a whole shitload of time in one group and then immediately jumping to spend a shitload of time in another group doesn't sit well with me.
