Merge by Distance and Vertex Weights of 2 separate Mesh Objects

Blender Version: 2.82a
Operating System: Manjaro Linux 64bit

I was helping someone troubleshoot some rigging/weighting issues and managed to fix most of the issues from this IMAGE in this DEMO.

However, the one thing I wish that could be faster is the fixing of weights near the seams (gap) of the 2 separate Mesh Objects. The current solution is to join the 2 separate Mesh Objects together and then merge those troublesome seams (vertices) together.
Separating the Mesh Objects afterwards will still keep those weights perfectly, but the process still feels too lengthy.

An old demo example:
A recent demo example:

In the future, would it be possible to use Merge by Distance as a way to quickly snap vertices together from 2 separate Mesh Objects?
Since these vertices are from 2 different Mesh Objects, obviously the vertices won’t fuse together, just snap. However, it would be convenient if there was an option to include weights as well.

If someone wants to turn this into an add-on, that would be great for riggers and weight painters.