I’m trying to do something similar and working on the approach, thought-experiment time while updates are installing. Constructing the belt geometry itself first is what makes sense to me. A pair of displaced closed guide curves exploded into segments then line connected between should work to help create a mesh or surface, maybe ruled surface.
Apply unit z constant force field for gravity, make the geometry into a solid object and check for collision with other objects. The rotation vector on the ends is tricky but ignoring the bottom may simplify things and allow use of constant field along the travel path between the conveyor ends. This approach doesn’t solve the problem of moving geometry but may work for animations and gives a basis for comparison, basically showing a sliding box on a surface that looks like a conveyor.
My updates are installed, time to go work through this more; moving geometry is my goal.
Has there been progress on other approaches?