I'd probably go with Henry out of those options. I think both can create a great Clash of the Titans war in their match, as seen during their exciting confrontation and immense brawl on Raw. Also makes the most sense from a storyline perspective. Lesnar "injured" Henry, Henry returns for payback against Lesnar, and there you have it. The strong possibility of mic wars with Henry and Heyman is also a must!
Wouldn't mind Langston though. Going up against Lesnar would be a huge rub for Langston and on top of that, it's a fresh match. Could see it being a very decent, near good match seeing as how both are two highly talented big man workers with a perfectly balanced blend of athleticism, speed, strength, etc. And the thing is, Langston doesn't need to win, he can lose but put up a fight and still look impressive after the match, and possibly get a standing ovation from the fans after the match. Much like Punk at SummerSlam last year.
Got no desire seeing it be Show. We've seen it plenty of times in the past to the point it pretty much wouldn't mean anything today. And I doubt a match between them now could top any other their work from the past. I'm also sick and tired of seeing Show constantly be involved in high profile matches at this point in his career.
vs 29 superstars in the Rumble match.
Honestly, what would be the point of that? Heyman clearly said that Lesnar doesn't need a Royal Rumble victory to get a title shot, since he already has a guaranteed title shot (which will most likely take place at Elimination Chamber). So yeah, putting him in the Royal Rumble match would just be nothing more than ridiculous booking, especially if he were to win it.