Here is a basic setup for stitching vellum cloth together using the weld seams feature on the vellumdrape solver.
Edge groups are assigned to the garment pattern pieces and define seams that will be stitched/welded.
The edge groups are run through a subnet to produce companion point group for the edge groups. The point groups are used for stitching seams. The subnet allows you to increase or decrease the cloth resolution independent of these groups, so it is more like Marvelous Designer particle separation in that respect.
The vellumdrape solver has been hacked to allow deforming collision geometry. All I did was disable the timeshift node which kept the deforming geometry locked to the start frame.
ap_basic_vellum_drape_vest_101518.hiplc