Yes, agreed. I will try to provide all the different mirror flavours.
I also have made some progress regarding topology-based symmetrizing.
The only obvious issue is currently that it needs a "seed" to work.
On some meshes this is very hard to define automatically, so I am thinking of a manual helper input where necessary.
Maybe someone knows whether there is a 3d tool that can display the vertex numbers of an .OBJ ?
Then one could "see": Aha, vertex 34524 corresponds to vertex 1475.