The problem with trying to build him back up is that he is already in a world title match that he is sure to win. The time to build him back up is gone as he is going to be THE guy on Raw now.
You say that...
But I wouldn't put it past the WWE to put the title back on
Brock & have him hold it until you know who is set to return.
I think he can easily lose the title to someone and move onto another feud. But not a midcard feud.
I don't know hey...I think Strowman was completely "borked"
by the WWE. Teaming with Alexa Bliss, Ember Moon & a
young kid, playing stand up bass, failing to cash-in his MitB...
although technically the Crown Jewel match is his second
cash in attempt.
At the SummerSlam 2017 Strowman was white hot & I think
the entire WWE audience was ready for him to be the Universal
Champion...but since then...its all been down hill.
BUT...that's just my perspective on the matter.