While the Japanese women's team is likely practicing their "MB1" formation at the upcoming World Grand Championship, I'd like to share my memory about the Argentine men's team in 2002 World Championship, who also had a "MB1" formation on court, though in a different way.
The Japanese coach quoted their new formation as "MB1" since they would have 4 wing spikers with only 1 MB on court. They're experimenting this formation because of the well-known fact that their MBs are too weak in the scoring element. Sakoda who's normally an OH with a high vertical jump, will fill up a MB position. She won't play quicks, though. Instead, she'd spike just like a wing spiker, but from the middle.
This news reminds me of a very interesting formation adopted by the Argentine men's team when they played at home the World Championship. Argentina then also couldn't find another good-quality MB to pair with Spajic. To compensate this, Argentina tried to fill up their firing power on court as much as possible with more hard hitters. Hugo Conte, playing at home at the age of 40 in his last tournament at NT, took the position of MB. However, he almost never spiked from the middle. Instead, the legendary Milinkovic, together with the powerful and versatile Elgueta, played as acting MB whenever Conte was in the front row.
Starting line-up: Weber (setter), Elgueta (OH), Conte (MB), Milinkovic (OPP), Bidegain (OH), Spajic (MB), Meana (L)
Legend: Re L/C/R (received from left / center / right), LH / RH (left / right-side hitter), P (pipe attack)
Milinkovic (LH) --- Conte (RH; Re R) -------- Elgueta (MB)
Bidegain (Re L) --- Spajic / Meana (Re C) --- Weber
In this rotation, Conte and Elgueta swapped their positions. Relieved from reception responsibility, Elgueta would start his assisted run from the sideline to play A or C quick.
Bidegain (LH; Re L) ----- Milinkovic (MB) --- Conte (RH; Re R)
Spajic / Meana (Re C) --- Weber ------------- Elgueta (P)
When Elgueta moved to back row, Milinkovic played as a MB. Milinkovic might have forgotten how to play A quicks, so he seldom attacked in this rotation. As such, this rotation is a relatively weak rotation for Argentina offensively, even if Elgueta still did not receive and could focus at completing pipe attacks.
Spajic (MB) --- Bidegain (LH; Re L) --- Milinkovic (RH)
Weber --------- Elgueta (P; Re C) ----- Conte / Meana (Re R)
Offensively, this is pretty balanced, with Milinkovic, Elgueta and Spajic in their usual positions.
Weber --------------- Spajic (MB) ------------ Bidegain (LH; Re L)
Elgueta (P; Re C) --- Conte / Meana (Re R) --- Milinkovic
Not a strong rotation offensively but at least with many attacking options (needless to say, Milinkovic would take a lot of offensive load from back row). The challenge is for Weber to run from the left sideline to the middle of pos 2 / 3 to set. He's short but was quick and skillful, though.
Elgueta (LH; Re L) ----- Weber -------- Spajic (MB)
Conte / Meana (Re C) --- Milinkovic --- Bidegain (Re R)
Bidegain almost never spiked from back row. His role on court is to receive in all rotations.
Conte (LH; Re L) --- Elgueta (MB) ------ Weber
Milinkovic --------- Bidegain (Re C) --- Spajic / Meana (Re R)
Although Elgueta usually did not receive in this rotation, he would still move to the right sideline initially. Conte had a challenging role in this rotation by having to perform both offensive and reception duties. Occasionally, Bidegain and Meana would move slightly towards him such that his coverage area would be smaller. Elgueta in this case would also participate in reception near the sideline.
A few interesting facts here:
1. Both Milinkovic and Conte were once MBs in their early career at NT. However, perhaps because of his old age, Conte was never asked to play quicks in this formation, even if he's positioned opposite to Spajic in the line-up. Milinkovic, who actually played quick spikes pretty well in the past, appeared to have lost his rhythm after playing OPP for many years.
2. Perhaps to resemble the rhythm of an OH, Elgueta liked to have an assisted run of long distance to play quicks. As such, in both rotations 1 and 6, he started from the right sideline to play A or C quicks, a bit like playing cross. The tempo was not as quick as Spajic's, but was still impressive and effective.
3. In all rotations, the formation seemed to be meticulously designed such that Conte had to move the least. When he served in rotation 3, he would serve from zone 5 and stayed there for defense afterwards.