#2 Do not sell Roman as a sympathetic figure
Roman Reigns is not a sympathetic figure. He has been given opportunity after opportunity to beat Lesnar, despite all his losses.
Even if this was in the kayfabe world, Reigns doesn't deserve the repeated shots he has been getting, including this recent No.1 contender's spot.
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Reigns lost at WrestleMania 34 decisively, but still got a shot at the belt in Saudi Arabia. He then lost clean to Bobby Lashley at Extreme Rules, but still faced the same man for a number one contenders match, which he conveniently won.
These repeated opportunities aren't given to someone who has been 'held down' by management. Sell Roman as he is, a cool character with a great look and great in-ring prowess, just like he had been marketed whilst a member of The Shield. He is a powerhouse, not someone who snivels at the fact that 'the system is doing him wrong'.
And on that note...