I have wished for the same thing - a match B to A or A to B with the ability to choose the master. You want identity of values, but still have two verts. RDS has the same weld function. I am still not convinced that the vertex modeler in Carrara is as capable as MFM. It does zoom better. But you loose the ability to get multiple groups into VM and still have them select by their real group. The other functions are more sophisticated, fer sur,