Sarevok seemed to die because his MINHP1 was either removed, or didn't get hex-patched in in the first place. Don't know if BP-WeiDU has anything to do with this.
With both of Rakhu's savegames, I had no problems getting Irenicus to appear on a NeJ2-BGT only install and using the AR0602.BCS Rakhu posted. This could spell out a compatibility problem --- BP-WeiDU again? I don't know, I'm just fishing.

Anyway, I've sent Rakhu an Auto-Save after the transition. Since most of the data is included in the savegame, there shouldn't be any major problems. AR0602.ARE might be a bit different from his version, but I don't think that will break going to NeJ2 or the main quest of Shadows of Amn. Here's hoping...