@DavidFlude
By no means did I want to sound disrespectful, when I talked about the books by Lane and Sawyer. I just feel that there are certain weaknesses that have to be addressed (and will be in my book):
Regarding Lane:
His coverage of the Lemberger is truly pitiful, even for yesterday's standards. Two pages (!) with mostly irrelevant variations for a critical line that has been known since the 1890s and that is played in about every 10th game? And on top of that, he states that the Lemberger can "easily be dealt with" by playing the Endgame Variation after 4 dxe5? Uhh...
In his chapter about the Ziegler he quotes old analysis from Studier that is simply flawed (yes, the one from the Rodriguez - Bricard game), which I suppose even Fritz 3 would have spotted back in 1995.
In addition to that, too many lines are covered with either irrelevant or long,
uncommented white wins where Black missed one or more signifcant defensive resources. And even if Lane did point out where Black went wrong, he did not offer any improvements and how White should react to them.
As for Sawyer:
I agree that he has done a great job collecting material; unfortunately at some places less would have been more, as he even gives ICC games where Black mouse-slipped - I just don't think it is necessary to cover every move Black is legally allowed to make at any time. Instead, more verbal explanations would have been better.
Furthermore, rather dubious white alternatives are often supplied with uncommented white wins, making them look valid and playable. One example would be the so-called "Kloss Attack" (8 Kh1) in the Bogoljubow Defence.
My last point of criticism is the same as for Lane's book: Sometimes he does not mention critical defensive resources for Black, even if he must have been aware of them.
I know that, given the above statements, expectations for my book are high now, but I am ready to accept this challenge. I buried myself into all kinds of BDG sources for about a year and, assisted by Rybka 3, I feel quite confident.
@papageno
According to my analysis, the Diemer Gambit is good enough for equality, but not more. But as DavidFlude pointed out, White can also play 5 g4.
Concerning the Hubsch, I don't know if my publisher lets me include options against the Indians as the amount of the material about the BDG proper is quite large (and I don't know if I get any lenience toward my page count) - I'll let you know when I know more