I finally got around to having a closer look

. I use another computer for analysis so I don`t have them here, but here is at least my thoughts:
I don`t believe in any opening-advantage in the lines with an early Bg5 by white. In the Shirov-Gurevich game I think black equalizes easily out of the opening. Maybe Shirov played it to get Gurevich ´out of book´?
The interesting games are the ones where white tries to kickstart queenside play with an early b4. Now there are some questions to consider.
* Can Black castle queenside?
* Should white play h3 or not?
* Should Black respond to b4 with a6?
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Maybe Black can castle queenside, but after b5 Nb8 the knight is not very active and white can pursue an attack with pawn-pushes (a4) or by piece play (Nbd2 then Qa4)
So my first reaction to an early b4 was to castle short or prepare short-castling. Now if white wants to go with an early b4 I think he should first include h3, because then immediate short-castling is not an option for black due to Ne5. So possibly blacks best line starts with bg6!?
According to my analysis black did best to include a6 against non-h3 b4 and exclude it against h3-b4, but I`m not yet sure why.
I`ll post some lines when I get around to copying them.