Considering that it will still be a while till the game release and also considering that it is unlikely PGI will provide a full-fledged tutorial for complete newbies initially it could be benficial to start a Wiki project for each House/Faction. Main benefit of splitting it up over having a single one for the whole game would be that it's easier to find the specific info that way.
It should incorporate "House Lore" (which can be done before game launch), some typical faction Mech rundowns, a pointer to the BT novels best suited to get more info about each house, the relevant official house-specific BT publications and maybe even a full rundown of the canon House units as a reference data base. Maybe some sort of news ticker to log memorable events which are both House- and game-related
All this could be done easily by some PGI/community interaction, I actually don't think PGI would have to do that much work. Pretty sure there'd be plenty of community volunteers to help with that. And surely beats PGI having to divert major manpower to write a "Manual" for each House/Faction. And what's in it for "us" beyond that?
Well, for once it would really make life easier for newbies who get a more streamlined reference about "their" faction. Also those who never dug that deep into the background "lore". Having them sort through decades of BT sources and material all by themselves could be a rather overwhelming experience.

And who knows, over time it might actually grow an extra part to serve as historical database to log noticeable actions in game. Where e.g. unit XYZ on the 22nd of November 3050 managed to capture planet ZYX. Thus ultimately serving both internal and external purposes. Of course one big Wiki with House-specific sections could do that job as well. Although if you make them House-specific, you could toy around some with different Wiki designs to give each more of a unique flavour.