Idk what that other guy is saying but yes, Gohan was never supposed to be the lead. The movie was always supposed to be about Piccolo.

It was later decided that they wanted Gohan to get some of the spotlight because they wanted to play off of nostalgia, hence why the movie contains Gohan, in his cell saga Gi, fighting a recolored Perfect Cell

Wollfe, Gregor, and Rex already had their stories in the Clone Wars Sequel (Rebels)

Those 3 move to the outer rim and live on a repurposed AT-TE as fishermen, until they the Rebellion; where Gregor is killed and Rex fights in the Battle of Endor.