So the solution I came up with using the FloatingPawnMovement and “Gravity” volumes was to add a second Box Collision to my GravityVolume class which only has X and Y dimensions and has a scale of 0 on the Z axis. This second box collision acts as a visual reference for a vector which represents where the floor is on the moving platform relative to the GravityVolume. Along with resetting the constraint to which the pawn movement is locked, I also set the origin of that constraint to this new floor vector component when the platform moves, which stops the pawn from drifting. To handle jumping and other non-lateral movements, I simply add an offset from that ground point. It seems a little limited, but it’s more consistent than any of the trace or physics solutions I could come up with.
In the future, I might trace from the GravityVolume down until the floor is met and generate a custom heightmap to lock the character instead of using a single flat vector. As it is right now, this solution only works on completely flat surfaces, which is okay for my project but might not be the solution others with similar issues are hoping for.