#4 Walter (and Imperium)

Although the faction was born in NXT UK, Imperium has undoubtedly made their presence felt stateside as well. Marcel Barthel and Fabian Aichner currently hold the NXT Tag Team titles, while Walter reigns as the NXT UK Champion. The only member of the group that does not possess NXT gold at present is former SmackDown Superstar Alexander Wolfe.
Despite their success, though, Imperium do not seem likely to make a move to the main roster. Walter, in particular, has made it clear that he has no desire to relocate to the US permanently.
Speaking to talkSPORT last September, he said the following regarding a move:
"I would go on the main roster at some point but I wouldn’t move to America. Moving to America is not for me. American lifestyle is not for me. No, I couldn’t imagine that. When it comes to that, I stay where I am."
Realistically, in order to be a regular part of either RAW or SmackDown, Walter would need to be based in America. Both the above brands combine monthly to produce pay-per-view events. NXT TakeOver specials, on the other hand, are far less frequent.
NXT is the perfect home for Walter
The lighter schedule of NXT when it comes to big events means that Walter is far better suited to the Black and gold brand and can continue to appear on both NXT and NXT UK - lending his unique star power to shows on both sides of the Atlantic.
Remaining in NXT also makes sense for the other members of the Imperium. Barthel and Aichner stand out far more in NXT than they likely would do on the main roster. The same can be said for Wolfe, who was barely featured during his previous SmackDown stint.