I would prefer to encode the collision information in the urdf even if it is a new tag. Given that it provides a section for collision geometry I would assume it would be good to support a variety of collision geometry types. A detailed mesh is usually not the ideal geometry for a collision geometry. It would be nice to expand this to not only support convex hull type but Multi-Sphere, Octomap, Point Cloud, Signed Distance Field, etc which are more suitable for collision checking. I am hoping for an answer soon as I have a deadline. If this is not something of interest to be added to this repository I will need to proceed with creating my own variant to be released with a new motion planning package.