There's plenty of examples of real bands producing entrance music for the WWE.
Batista used "I Walk Alone" by Saliva
Chris Jericho used "King of My World" by Saliva
Dudley Boyz used "Turn The Tables" by Saliva
Triple H uses "The Game" by Motorhead
Evolution used "Line In The Sand" by Motorhead
Randy Orton uses "Voices" by Rev Theory
Hulk Hogan used "Voodoo Chile" by Jimi Hendrix
Christy Hemme used "Walk Idiot Walk" by The Hives
I think it really just depends on which wrestler WWE is willing to spend the money on. They'd either have to either pay an artist to write/perform a song for them, or pay so the artist would allow WWE to use one of their tracks as an entrance theme. I think WWE would rather write their themes in house if possible, as surely it would be cheaper to get Jim Johnston to do it than paying Motorhead to record another song, but sometimes they want to do something a little different, or are willing to splash out on a band to give a particular wrestler a boost and a new theme.
And they all cost shit loads of cash....
Voodoo Child cost them over half a million dollars to use for about 3 moths...and didn't do anything to help Hogan, it was just an ego trip for him to make Vince spend the money.. to be fair "Cult Of Personality" was just that for Punk too, but it worked and is now indelibly linked to him.
WWE won't spend if they can have Johnston or a house band "appropriate a song" look at Cesaro's first theme or Adam Rose's themes so far... all are basically variations of "Chelsea Dagger" by The Fratellis... this is not a "big band" it wouldn't have cost them much, but they still went with the cheap "soundalike" versions...
Bray isn't changing, he has his "guy" now, even if Crozer comes up with a new tune for him, he won't change the formula... but they did change one thing, they went from "Time Is On My Side" to "He's Got The Whole World"... one is in the public domain, one is a Stones song and thus expensive...
It's interesting to see the difference real music makes, there is a version of Mania I out there with all the original music intact... Born In the USA for Windham and Rotunda, Eye of the Tiger for Hulk and T... Another One Bites The Dust for JYD...even the old links/themes for WWE shows was "Modern Love" by Bowie... massive difference in credibility... but that cred costs more than WWE perceives it is worth... for every dud WWE theme there are 3 or 4 classic ones that do fit... Barrett has the Manic Street Preachers offering a theme for him cos they like him and they are his fave band (his tattoo is their lyrics, would seem a match made in heaven) but Vince don't let it happen... Band would probably do it cheap/for free but labels and publishers get in the way...
I can see them throwing some money at Reigns for a theme to restore him after the injury... Can't quite see them doing it for Ambrose cos he is "plan B"...If they could get the rights, a version of "Sympathy For The Devil" would be perfect for him...and I would love to see Bryan get to use "The Final Countdown" at Mania.. Next real opportunity I think is Neville, he is a Geordie... for some reason I can see AC/DC (with their fellow Geordie lead singer) lending a theme to him... something like Shoot To Thrill or a new track would fit him perfectly... It'd be the kind of thing someone like Brian Johnstone would do, and Vince or Trips would get behind cos they're "big enough"... would certainly help Neville become A-List...