If they were smart - they are not - I feel like they should go with:
Lesnar vs. Strowman
Reigns vs. Goldberg
No one wants to see Lesnar beat Goldberg, and it doesn't do anything to have Goldberg win another squash-type match over Lesnar only to disappear for 3 months. But everyone wants to see the two immovable objects collide.
And then nothing would make WWE fans more ecstatic that watching Reigns get squashed by Goldberg.
EDIT: I feel you can easily set up Lesnar vs. Strowman in the Rumble. Have one of the guys dominate for a while, maybe clear the ring etc. Then have the other one eliminate the one who dominated, maybe in a dirty way. Eliminated one goes on RAW the next night, promos how he was eliminated dirty and wants a one-on-one match at Wrestlemania. Bingo.
Crowd would eat up a Strowman vs. Lesnar match, and I'm not sure what other storylines are left for either guy anyways.