#4 Finn Balor

Just look at this picture above! Having Finn Balor in The Shield would just double his stock. The first ever Universal Champion hasn't had a great 2018, but since the beginning of 2019, he's showing signs of climbing back to the top of the mountain.
A great way of achieving that would be him joining hands with The Shield. Imagine the Shield celebrating in the ring after a victory, and then Balor comes out and attacks Dean. Seth and Roman try to separate them, and then "too sweet" they all beat up Dean Ambrose.
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Finally, Finn reveals himself as the new member of The Shield. How nostalgic would that be!
#3 Samoa Joe

Ever since coming up to the main roster in January 2017, Samoa Joe has been pretty much lost in the mix. He's still finding a way to step up and become the "next big thing".
Having him join The Shield might just serve that purpose. More than that, it can lead to a lot of amazing storylines and feuds in the future. At some point, Joe can start referring to himself as the PowerHouse of the Shield, leading to a feud between him and Roman Reigns.
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