Well, 1. g3 e5 2. c4 of course also transposes to Marin's repertoire choice, in GM3.

If going for this I could reasonably see 1.g3 being the move order. Sort of surprised a tricky 1.g3 repertoire hasn't been bandied about somewhere.

Well to be frank, I do not have a preference for a particular set up. I agree this is a maze of transpositions, this is why I am looking for an expert insights into this scheme of development. 

I mean, take 1.Nf3 for instance, Kramnik had his own pet lines, because he tried to thrive for certain types of positions. But not everything about 1.Nf3 has to be 'kramnikian'. Has anybody tried to put up a coherent repertoire starting this way? A repertoire with its own 'philosophy', coherence, the same persistent aim.

I could try to compile various books, but if anybody has already done it, I am curious.

On a personal note (Class A player),
I like having a flexible position, mainly with a strategic character. 
I like having a foot in the centre or fighting to have one, for instance by keeping pawn breaks at my disposal to counter at the right time or to dislocate my opponent's structure. 
I hate bad bishops (and have a tremendous score against the KID).
I am not so keen on gambiting right out of the opening, but absolutely willing to do it in the middlegame (positional and exchange sacrifices are fine for me).
I often outplay my opponent in the early middlegame (searching and building advantages) or in the endgame (piece activity).

It'd be a horrible book to try and write Utterly enormous choice for black and transpositions absolutely everywhere.