According to the July 2002 issue of Roundel, Joji Nagashima designed the current E39 5 series. Joji is also the designer of the Z3. The E38 7 series (1994-2001) was designed by Boyke Boyer, not Nagashima, despite some of its similarities to the E39.
The new direction of BMW design is being led by Adrian van Hooydonk (the new E65 7 series and Z9 concept car (which came out in 1999, complete with the big butt trunk now found on the current 7 series)) and Chris Chapman (X5, and the X Coupe and CS1 concept cars).
Of course, Bangle is in charge overall today. Most of the new designs emerged from a six month creative brainstorming workshop in 1996 called, "Deep Blue." The concept that emerged is what Bangle calls the "new aesthetic bandwidth." Bangle joined BMW in 1992 from Fiat. He grew up in Wisconsin(!) Evidently, Bangle is a strong car enthusiast, and a very good salesman. He used the latter skill to persuade (hoodwink?) BMW management into its current design direction. Read more about this in the July 2002 Roundel, beginning at p. 40.