I did a quick test with the bodice, that is made of triangles. The only problem that I found was with the shoulders movement. The collar present a little problem and chest and abdomen works well.

What I found with your mesh has nothing to do if is made of quads or triangles. First problem is that the mesh is not welded and so, it can sepparate the partes with some bendings. The joints for the collar need a small adjustment and the joints for the shoulders are wrong, the bending of the shoulder have no effect on the collar and maybe chest too and it must have in this cloth.

Beside this, is a nice cloth

Stupidity also evolves!