#2 McIntyre is not a part-timer
The Universal title is the most prestigious belt on Raw. Brock Lesnar is the current Universal Champion, but he is a part-timer. The WWE Universe gets exasperated when the champion does not appear regularly. As a result, the ratings get affected.
Brock Lesnar also participates selectively in PPV's.
Charlotte Flair to return and wrestle a CURRENT CHAMPION?
He did not fight at TLC which was the last PPV of 2018, and Lesnar's last match was at Survivor Series where he defeated Daniel Bryan.
Lesnar did not defend the Universal title at Survivor Series, as it was a champion vs champion match. As a matter of fact, he has not defended his Universal title after winning it at Crown Jewel.
Drew McIntyre appears on Raw every week.
WWE has been pushing McIntyre as a top guy, and he could be a believable candidate to pin Lesnar. McIntyre is a full-time wrestler who could defend the Universal title on every single PPV. Moreover, the fans will love to see the Universal Champion every week, and it might help to improve the ratings.