Hmm. Well you certainly seem to know your subject matter and based on the other books I have by you I really like the way you present useable information rather than just waffle. The page count is high but the quality of content matches. I like.
I don't know if you already had this in mind but how about a chapter on legendary artifacts of the gods and such? Excalibur, the Ark of the Covenant, Thor's hammer...that type of thing. Might be useful to build games around or use in high powered games?
Also if this is going to Kickstarter...on a purely selfish level...how about the add on or stretch goal of a print run of the 6th Edition Core rulebooks? They are next to impossible to get and priced stupidly where available. The 'Complete' versions...I understand the publishing logic of...having to keep entry costs to players low etc but with a Kickstarter print run you'd be financially covered...get enough money to do it...it happens...don't...it doesn't and you don't get left with a loss making pile of stock. Just a thought.
Anyway, I wouldn't normally buy a book on gods etc because I can google most of the information I want but I trust you would save me a whole mountain of trouble and be better informed than most of the 'net. Good luck.