I think they can do it. Block him in between an ice barrier and Bartolemeo's barrier, also freeze him solid, while Sanjuan throws 6 pieces of kairoseki near Imu, one further away, then Law uses room to switch Zoro and Aokiji with a piece of kairoseki, Aokiji is switched with the one further away from the rest of them. Then Zoro puts the remaining kairoseki next to Imu's frozen body to stop his fruit from working, then Law switches him back out with the kairoseki, Aokiji freezes the kairoseki around Imu from a distance, then gets switched out, then Sanjuan Wolf throws some kairoseki the air, Aokiji closes the top up with ice, the kairoseki in the air into the space first. Then Law switches Imu's heart with a piece of kairoseki. Then Sanjuan throws it in the ocean. Then Franky builds a freezer around Imu, powered by the sun and by a wind turbine and by Jinbei running on a hamster wheel.