It's hard for me to imagine Luffy interacting with a character like Imu. Just like how he reacted with disinterest when Emet called him Joyboy, I can't see him caring too much about the overarching plotline of Joyboy vs Imu, besides him obvious hating Imu for kidnapping Vivi and maybe for genociding people. Imu will see Luffy as a proxy for Joyboy, but Luffy won't see himself as a new Joyboy.