#15 Universal Championship: Brock Lesnar (c) vs. Seth Rollins
Main event it might not be, but it's still the most important match on the card. At stake is the future of Raw. If Seth Rollins wins, the red brand and the Universal title get to hit the badly-needed reset button and begin the long process of rebuilding from the rubble they've been in for the past year (or two, in the case of the title). If Brock Lesnar wins, the dark age, the wasteland, continues.
Consequently, it will come on late, in the 15th or 14th spots.
#16 Winner take all: Ronda Rousey (c) vs. Charlotte Flair (c) vs. Becky Lynch
We already know this match will be the main event. It's still a cluster and it will still be a relief when it's over. WWE threw away a potentially magical build to throw Charlotte in, which makes it less than it could have been.
Becky Lynch will probably emerge the victor from the match, though, and hold both titles aloft, which will be the best WrestleMania ending in years.