I really like the idea, as an avaid Magic the Gathering player I have always been fascinated with the Ravnica sets, the new one is coming out very soon too!

Pre release here i come.
anyway, I thought the best comment I could give would be for you to look into the Color Wheel Theory, since not only is it essential to understanding the duel color guilds, but also we Paint models! The colors could easily come up within your colors in very interesting ways.
There is a great article on the subject by Mark Rosewater,
http://www.wizards.com/Magic/Magazine/Article.aspx?x=mtgcom/daily/mr205
I recommend you check it out for any ideas and such.
Alsomaybe change out some of the names, no need to have all the same names, just the main ones i would say, and keep the other ones lieke Agrus
Kos to the sidelines (scout leader or something)
Def with characters like the Dimir guildleader who could easily just be Tyzeech or another current Canon character to bring this chapter deeper into the world of Warhammer
40k.