Bulk merge weights tool

I have been trying finding solutions for bulk merging weights for a few days now as of time right this, but all of the solutions for merging weights only involved between two bones and doesn't really allow me the merging of many bones at once.

There’s a plugin in Max that is called SkinUtilities. This plugin can extract the skin data from a selected mesh and puts the data into a dummy mesh and it can import this mesh containing the data into another mesh.

When importing this mesh, it will prompt with this menu:

From that point, you can map in the Source bones into the Target bones and remove the Target and/or Source bones if they are not needed for the importing.

Note that I mapped up to three bones into two of the target bones. I can merge the weighting of several bones into weighting of just one bone with this way.