Let me try break this down real quick:
New record eliminations at Royal Rumble and last eliminated by Bryan or Punk
This could happen easily, and I agree it should be done in the 2014RR, have him eliminate Batista too or be eliminated by him, throw some big names in his eliminations not just mid-carders and jobbers.
2 eliminations against the Wyatt's inside the elimination chamber before being eliminated by Bray with the help of Harper and Rowen( H and R won tag titles at Rumble)
Not sure about this one, but I'd let it roll out.
Reigns takes a loss to Taker at Mania in a close match who is getting revenge for the attack
Yes, I'd love to see this and really let reigns take him to the limit and really let people believe he could have beat the streak, this can create more tension/jealousy in the Shield if they already haven't split up by this point.
Shield break up after Mania with Reigns turning face and Ambrose and Rollins staying heel
Easy one, have this start the NIGHT AFTER WM as the crowd is gonna be hot for the start of a new 'WWE Year' and have Ambrose and Rollins attack him and say he's no longer part of the Shield, let them go as far as taking his 'Shield Attire' of him (like when Bully Ray took the kuttes from ex A&8's members). This also gives Reigns his own identity by having to wear a new wrestling attire.
Reigns wins a triple threat against Ambrose(lost US title to Bray at Mania) and Rollins in a cage match at Extreme Rules
Have Reigns decimate the match near to the end and climb over the cage to win because he has time.
Reigns wins against Ambrose in a LMS match at Payback
Have Rollins run-in for Ambrose and and Reigns has them both laid out for a 10 count.
Reigns wins MITB at PPV and cash in later that night and then a long title reign
(IMO, with only one champion to cash in on they should bring MITB back up to WM but anyways...) have Reigns win this match but don't cash in, he's built himself up yes, but don't cash it in that night, cash it in at a Summer Slam but have him lose (to boost the unpredictability of a MITB winner gaining the championship...) in a really long match (hopefully the champion by this time is a face and...) Reigns can earn the respect of the faces(after all, he did terrorize them all as part of the Shield) and win a another match to get a shot at the WWEWHC by Survivor Series and win the WWEWHC from whoever is champion (in another epic match...) and hold it up to WM31 also giving him some credibility for doing something major at all the 'Big 4' PPV's in WWE.
Beats Taker in a streak vs title at Mania 31
By this time Reigns is still champion (obviously) and this time around, HE wants the match against Taker to have another crack at ending his streak, Taker says fine as long as it's for the WWEWHC blah.. blah.. blah.. Reigns says yes, they shake hands, the crowd pops for it, at WM Reigns has all this "big match experience" and can "go the distance" with the UT, Reigns wins the match (...because we all know that Taker can't carry the belt when he wrestles once a year and...) ends the UT's unbeaten streak at 22-1 (which is perfect because 22 looks unfinished).
And that's how I'd book Roman Reigns over 2 years.