Most of those guys are way too old for the WWE at the moment, and really wouldn't add anything to the product. Imo.
As far as If Brock were to return, i think they continue with Undertaker vs. Brock to headline WM 27. That would be Brock's first match back to the WWE. Brock returns at Mania with Paul Heyman and beats the undertaker cleanly at Wrestlemania. He then goes on to win the WWE one month later. Upon winning the belt from Orton (or someone) He continues to defend the title for a lengthy reign against Orton, Cena, Undertaker.... HHH makes a big return at SummerSlam to challenge Brock, in which they face off at Survivor Series. AFter defeating HHH, HBK returns to challenge Brock at Royal Rumble cause he has one match left, but cannot get the job done. Brock holds the gold to WM 28, where he is challenged by the underdog now face CM Punk, who goes on to pull off a major upset and defeat Brock for the title.
As far as the Rock goes....I'd have Miz being the Miz for a while and maybe throw a shout out to the Rock about his bad movies in the November timeframe. In the December timeframe i'd record a prerecorded comment from the Rock about the Miz, which results in the Miz continuing to talk trash about the Rock. Finally in Jan, on Raw the Miz will be talking and all of a sudden the music hits "Do you smell what the Rock is cooking?" The Rock comes out and cuts and classic promo on the Miz. The Rock punks out the miz, and as the Rock is walking away Miz challenges The Rock to a match at Wrestlemania. Rock doesn't accept or decline, but in Feb he will say he will be at Wrestlemania. SO it will be booked as a Miz/Rock confrontation. On the Mania show, Rock comes out ready to wrestle and defeats the Miz, in his return. But the fued isn't over there as Miz makes up some reason why he was cheated. The Miz adopts the People's Champ gimmick, as the Rock takes a some time off after mania. The Rock returns yet again and this time The Rock challenges Miz at SummerSlam. This time raising the stakes. The people's champ gimmick on teh line. THe Miz wins. After the match the Miz extends his hand, and thanks the Rock for a great match. (Face Turn for the Miz) The Rock and Miz then continue to team together, and win the tag championship. Around the Royal Rumble teamframe.... The Rock turns heel on Miz and lays him out, saying He's not a tag team wrestler...he wants the Champ...Cena. (So i'd book some book and forth stuff in late 2011 to lead to Rock/Cena) The Rock injuries Miz who takes some time off. Wrestlemania 28 features John Cena (The Champ) vs. The Rock. THe classic Ref bump, Miz returns from injury tries to hit the Rock with a chair, but hits Cena. The Rock wins the champion at 28.
So WM 27
Brock vs Undertaker
Miz vs. Rock
Orton vs. Cena (World Championship)
Summer Slam 2011
Brock vs. Orton (World Championship)
Miz vs. Rock II "People's CHamp
Survivor Series
Brock vs. HHH
Rock/Miz vs. Tag Champs
Royal Rumble
Brock Lesnar vs. HBK (World Championship)
Rock turns heel on Miz and wins Royal Rumble
WM 28
Cena vs. Rock ( WWE Championship)
Brock vs. CM Punk (world Championship)