WWE superstar The Miz has a Plan B in mind for Conor McGregor after he fights Floyd Mayweather ... and it ain't the UFC!

We asked Miz if Conor should join him in WWE after MayMac is a wrap -- and his answer was a resounding HELL YEAH.

Miz told us McGregor can "talk the talk" and "walk the walk" -- and that his skills on the mic would make him a huge star in the squared circle. 

But even though the WWE intercontinental champ LOVES Conor's shtick ... he ain't exactly sold on him out-boxing Floyd.

McGregor's got plenty of options after taking on TBE, of course ... but he might wanna avoid the WWE after trashin' Brock Lesnar and most of the roster last year.

THEY'RE NOT THE REAL DEAL
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