robus
Lowcountry Low Roller
I would like a FRCS, but do not need one per se. I am ambivalent to SCaG, as I only use it for the crunch (love that Oath of Crown paladin quite a bit), but not much else.
I think instead of a book what would be really super amazing awesome would be an online resource with wiki entries and some such that people could utilize. You could even have it editable by anyone with curators. It'd be like Pottermore for the Forgotten Realms! That way they don't have to publish a book that will inevitably disappoint some who want it more comprehensive and be ignored by those who don't want it.
The website/resource wouldn't have any crunch, just stuff you need to know drawn from all the FRCSs. Click on Daggerford to see the different demographics throughout the timeline, what the hot spots are, NPCs, and so forth.
And this: http://forgottenrealms.wikia.com/wiki/Main_Page I'm sure isn't sufficient ?