Sounds like an awkward harmonization of the Johannine and synoptic timelines. Just a few comments:
(1) It would insert a whole day (the weekly sabbath) between Mark 16:1 and Mark 16:2, when there is no indication thereof in the text. The most natural reading is that when the sabbath was over (i.e. after 6pm on Saturday) the women bought spices, and then they went to the tomb at dawn the next day (Sunday a.m.).
(2) The sabbath described in Mark 16:1 is not designated as a high holy day or the Passover itself, nor could it have been because it had already passed. Mark 14:1 places the anointing of Jesus in Bethany "two days before Passover" and then the preparation of the Last Supper (i.e. before 6 p.m. on the same Gregorian day that the meal occurred after 6 p.m.) occurred "on the first day of Unleavened Bread, when they would sacrifice the Passover lamb" (Mark 14:12, an event that John places a day later). The "sabbath" which preceded the women's buying of spices was not the first day of Passover (which was celebrated as a sabbath).
(3) If the women really bought the spices "when the sabbath was over" (Mark 16:1), this implies that they would have done this on Thursday evening (after 6 p.m.) and not Friday morning. But in either case, we would have a very awkward situation of the women waiting a whole day to anoint the body and even missing their chance to do it that day, letting another whole sabbath day pass while Jesus' body rotted in the tomb. It is exceedingly unlikely that such a thing would have happened, especially in light of the Jewish tradition that the body must be anointed before the third day (by which the time the body has begun to decay and the spirit leaves the body for good).
(4) It does not really resolve the conflict between Mark 14:12 and John 18:28, 39, 19:31. It also resolves the conflict between Mark 16:1 and Luke 23:56 by inserting a whole day in between Luke 23:55 and Luke 23:56 (without any justification from the text), even though the "sabbath" mentioned in v. 56 is surely the same one mentioned in v. 54.
(5) It would necessarily date the Last Supper before Nisan 14 (i.e. Tuesday after 6 p.m.), which accords to some extent with John (which does not construe the meal as a passover meal) but which conflicts with Luke 22:1-13.
(6) If I am not mistaken, there are other early Christian traditions supporting the traditional chronology. The Asian quartodecimians (including Polycarp of Smyrna, who was born in a Christian family in the 60s AD) placed the Christian passover (Pascha) on Nisan 14, and the Epistle of Barnabas (early second century AD) construed the resurrection as occurring on the "eighth day", i.e. "Sunday" (i.e. after 6 p.m. on Saturday, after the sabbath was over). Similarly, the mid-second century AD Gospel of Peter placed the resurrection "during the night before the Lord's day [Sunday] dawned" (9:1), and the soldiers had to "rose the centurion from his sleep" to report the resurrection to him (10:1), implying again that the resurrection was not construed as occurring near sundown.
(7) Finally, the harmonization does not resolve the apparent conflict between Jesus being buried "for three days and three nights" (Matthew 12:40) and the tradition about Jesus being raised "on the third day" (1 Corinthians 15:4), which is a shorter length of time.
