#3 Braun Strowman vs Brock Lesnar vs Roman Reigns
The third possibility is for Strowman to cash-in during a potential match between Roman Reigns and Brock Lesnar.
In similar fashion to Seth Rollins' cash-in during the Reigns vs Lesnar match at WrestleMania 31, Strowman could enter the match and snatch the Universal Title away from The Beast.
This would be a way of getting the title off of Lesnar without him actually being involved in the decision of the match.
If WWE did indeed want to protect Lesnar and have him come back and feud with Strowman, having Braun pin Reigns for the belt could give Lesnar that sense of injustice for a future clash. This route could also set up a rivalry between Strowman and Reigns in the subsequent period.
With Lesnar expected to leave soon, a clash between the 3 top stars on RAW at SummerSlam could be the perfect end to The Beast's reign as Universal Champion. This could be the blow off match that elevates Strowman to the next level whilst keeping Lesnar strong.
WWE could ultimately decide to hold fire on Strowman's cash in, but given Lesnar's expected departure and fans not buying into Roman Reigns, the decision to put the title on Strowman could be done sooner rather than later.