Evidently this is not too common.  I finished the repair last night and
thought I would post my "fix" for the archives.

Each spot weld was drilled with a a 3/8" drill, just through the outer door
skin, not through the component.  I then cleaned up the area around each
hole with an angle grinder.  A dremel was used to clean up the exposed
metal under each hole.  Clamping the hinge assembly to the door skin, each
hole was then filled using a mig welder.  Surface grinding, primer and
touch up with some colour match paint finished the job.  Spot welds that
were repaired were 4 above and 2 below the lower hinge (where it inserts
into the door) and then about 8 that hold the hinge subassembly to the kick
panel of the door.  You can see three of the spot welds normally in the
exposed metal area right at the bottom of the door ... opposite the
footwell step.

Kind of scary to think how a factory mistake like this would manifest
itself in a more critical area of the van.  I've never seen this problem in
any vehicle before.