Probably the best way to predict how the Japanese court would evaluate the value of the bitcoins would be to use some Japanese precedent, rather than American precedent. 

Yet if the precedent is unclear, and the calculation of value would cause inequitable results, then stakeholders can propose other value calculating methodologies.  Certainly a lot of stakeholders would like to receive their value from GOX in whatever asset that it was held.  So if they had bitcoins in GOX, then they should get bitcoin back.  If they held fiat in GOX, then they should get fiat back... and the ratio of how much they get back would depend upon the total solvency of GOX.   A liquidation would likely get them less than 20% of their holdings; however, a rehabilitation would have the potential of recovering a higher percentage, over time (even though possibly the initial payoff amount may be low with a rehab).

Personally, to me, it does NOT make any sense to pay off stakeholders in any other currency (or asset) other than what they were holding or to attempt to value it in any way - b/c some stakeholders were choosing (on their own - maybe somewhat coerced on the circumstances) to trade btc and fiat.