On this page (
http://www.basiscape.com/works_cd2010.html?index=8 ), the composers are tagged as （作編曲）, so I think we can safely fill in their names in the "Arranged by" field too. Also, I'm dying to get an official track-by-track composer breakdown for this soundtrack. It gets a solid 5 out 5 from me. I love it!
From website:
Music by Basiscape
岩田・並木・金田・阿部・上倉・千葉・工藤（作編曲）