Cool addon with great potential!
I tried to test it in production scenario (bit more complex game models). Few issues:
a) Metric scene scale is not respected. The imported model is MASSIVE and fails to make anyhing meaningful.
b) Using Booleans to create weld is not always possible, infact rarely on model I tested.
Ideally you should let User create manual curve and use raycasting or some other method of quering to align tilt of curve so welds are rotated correctly.
c) Modifier stack or source object data can get messed up (initial selection, pre running weld_op)