There's supposed to be 1000s of books of scripture. Just do what the minmatar did with voluvals and clans and such and make things up. If people like it, those things will get used, if not, they'll be set aside.
"Making things up" is what caused the mess in the first place, because people were "making things up" by using RL religion as their source. So that sounds like a pretty terrible idea to me.
Even without that mess, there's another factor I think you're overlooking: just because it works for the Minmatar does not mean it will work for other cultures in EVE. The Minmatar, by their very nature and what we've been given by CCP, are a good candidate for the "throw shit at the wall and see what sticks" method. The Amarr, however, are not. In an Empire where the easiest measure of who holds more power than whom is where they are in the family tree, where there is a single state religion with no legal alternative options, and a fairly rigid caste structure, throwing shit at the wall to see what sticks is not an appropriate tactic.
This is a case where if there are holes, CCP needs to be the ones to put up netting or fill them in outright, because the last thing the Amarr need is for their religion to be even more like modern Christianity with thousands of different interpretations that nobody agrees on. In the Empire, only the TC-approved interpretations of Scripture are valid. Making shit up with this case, in my opinion, does amount to godmoding - because if you claim something is a valid, TC-approved interpretation or piece of Scripture, you are basically claiming that anyone who disagrees with you is in violation of Amarrian law. And that'll go fun places real fucking fast.
When you're talking about your own sect or offshoot that doesn't affect anyone except those who opt into it, fine. Make up all the shit you want.
But don't try and do that with the largest religion in the cluster. That's a lot of people - NPCs included - for whom we do not have the right to dictate their actions or beliefs.
This.
TL;DR - Basically making stuff up is a legit means of creating content and RP, but you need to consider the situation and context of your creation otherwise you can easily fall into god-modder territory, and that is nasty crap we don't really want anywhere.
Basically, making stuff up is only valid in a number of situations. I'll make another example of something that is not a valid candidate for making stuff up about;
The official means the Federation employs to solve situations not covered by any PF so far. Anyone can claim what's standard modus operandi in some Federation member nation on some planet somewhere, because the odds that CCP will ever make something that directly contradicts this are fairly slim.
But no-one can come and claim out of thin air that THIS IS HOW IT WORKS AND EVERYONE KNOWS IT OR CAN LEARN ABOUT IT because there is no way of knowing for sure, because it's not in any official PF, and thus, your making shit up that should be known to billions of NPC's and hundreds or thousands of players that no-one else knows, and your basically telling all those players what they are supposed to know.
Telling Synthia that you have viable arguments regarding pieces of Imperial Scripture that you yourself recently pulled out of your ass is not only unfair and god-modding, it's very, very rude. There is no way to counter this except to play along IC on a significantly weakened standpoint (because your character now suddenly know stuff that no-one else did and acts on it) or or to argue that your claims are false to begin with, and that goes down the road of 'you!/no you!' level of argument. It's not RP at that point, it's two players arguing in an IC format about stuff you have made up on the go. Stuff that supposedly everyone else knew of from before, or could easily go find out if they wanted.
The huge problem here, I think, is partially a lack of... meat, on things like the scriptures. There are supposedly thousands of books in this fictional collection of holy works, as mentioned. But we can never expect CCP to write it all down for our enjoyment, much like we can't sit and wait for them to flesh out all the ins nd outs of every Federal, let alone Imperial, world. It can't be done.
But we can limit ourselves to taking only the known, PF revealed Scripture into context when we RP. We have to, because making up anything in what's supposedly a well-known and easily accessible codex of life, the universe and everything to trillions of humans is, sadly, going to spark this kind of nasty situation.
Making stuff up on your own is perfectly legit, but one has to consider the context and the situation at hand. Needless to say, balancing this freedom of creativity with the desire to avoid god-modding is not simple at all.
*EDIT* I forgot, I was going to add this...It would be in our better interest to ask CCP's people who are responsible for this to kindly see if they can flesh things out a bit more. Using the Scriptures as an example, there is WAY to little of it in regards to what's supposedly there. The Scriptures supposedly cover every possible aspect of the Imperial way of life. The desired means of dress, grooming, eating habits, transportation means, warfare, trade, worship, child raising, proper maintenance rituals for pretty much anything can can imagine and so much more.
Only in regards to the Amarrian Empire there are so many major and minor things that we don't know about. Freedom of creativity is great, but many basic questions remains unanswered. Then there are all the OTHER factions... In short, I feel like we should have a 50/50 kind of situation in regards to what kind of major info about... anything... is filled out, and what we have to make up ourselves. Currently it seems we barely have 10/90 in favor of the unknown. That's pretty thin.
How are they going to do this? I don't know, but CCP's folks might. Perhaps they can look over and approve more of the good player-input, like Kat's "Greatest Fan" story. That was a great piece, as well as very universe-friendly. I don't think it would hurt to make CCP's basic ideas behind the various factions known to the players and have the willing and talented among them help them out by fleshing out some more stuff. Obviously, CCP would have final say about what get to be canon in the IP-protected fictional universe they created, but I for one would not mind at all getting PF fleshed out a tad more.
Also, note: This is supposed to be productive input and not offensive or aggressive in any way, other than getting my point across. If it's borderline violation of any rules, let me know and I'll edit it.