Commercial WYE WYE Transformers do not provide access to all 6 terminals of the primary or secondary windings. They have the common terminal connected internally and brought out as a single connection, so it is not possible to do what you propose. However, if all 6 terminals of, say, the secondary were available, the result would be an unsymmetrical phase relationship with the 3 phases separated by 60 degrees instead of the normal 120 degrees. If the normal phase sequence is A-B-C, then the new (Unsymmetrical) phase sequence would be A-C-B, with a 240 degree gap between C and B.