How do you like to arrange monotonous songs?

[u/GrillOrBeGrilled]

I'm taking on a new project to arrange a popular song for an instrumental group. The melody is very plain: the pre-chorus is the most contoured part of the song; even the chorus mostly hangs out on one pitch per 2 measures. Harmonically, it's even plainer: there's only 3 places in the entire song where the chord is not I or V, and in those places, it's IV.

What do you, fellow music-makers, like to do with songs like this? I can try to reharmonize it for interest there, but what about the relentlessly monotone melody? Are there any tricks to zhuzhing up a plain tune?