After a complete afternoon of a terrible fight, I surrender. A full custom configuration takes too much time, even starting with BetterWB. I almost made no progress (installed virusZ, a few libraries, and a half working version of Dopus).
I'll go for a ClassicWB lite version, and keep it as is. Otherwise, next year I'll still be struggling with workbench configuration (I know it's a hobby for a lot of amigans, but not me I'm afraid).
thanks anyway, BetterWb still a really cool pack !