I can elaborate more on rules and what distinguishes them from the systems you are referring to (improvisational magic, classes that are though traditional tropes handled differently with the introduction of the paths, the way resources and backgrounds are handled. Yes they do have a strong traditional RPG tinge, and I'm not looking to get away from that entirely)... but onto the other things you said that honestly stand out more to me and might be more useful to discuss in this particular case.
Your comments on the setting (and criticism of what you like and what it's lacking and what elements are weak) are what I LOVE to hear, and I am actually considering doing a book that is pure (or close as can be) setting, and maybe with some simple adaptations for games like Fate or something else (I'm not really a fan of Savage Worlds but that's neither here nor there). Why? Because I agree there's a lot more meat to be added to the setting and I'm probably much more likely to get people interested in it then rules (though I have been having a blast with the rules and do want to continue refining and improving them). You are exactly the sort of demographic I imagine I would be having to target if I am indeed to branch out and do a setting sans-rules book (or a setting book with some basics of how to adapt it to the rules of your choice book).
Now that all said, my intent to support a system-free book or other systems is very very much in an infant stage at this point (I didn't really come into this thinking I'd even bring it up, but it seems to be a worthwhile subject). If I do support a specific system with this I am leaning towards Fate, at least for the first one... I may branch out from there (though I think supporting too much is probably going to amount to biting off more than I can chew) but honestly, I'm not sure what other systems I'd want to support at this point (there's far too much PF/3.5 material out there all ready, and again, Savage Worlds isn't my cup of tea, so probably neither of those). If you have suggestions for other systems I should support (and again, I'm a bit worried about biting off more than I can chew with too many systems) I am open to looking into some.
I'll look over what you've written a few times and make a list since it looks like there's plenty of seeds in it for me to pick and elaborate on.
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OK starting to expand a bit
On factions: I'm actually torn on them. When I started writing, I wanted to keep them more madeup factions.... but you are right there's a TON of fascinating real world groups. I may drift away from the madeup ones (aside from the Blood of Adam and Sisterhood of the Phoenix) and towards real world ones, especially as I do more research... plus the real world ones all ready had plenty of motives and schemes that I can twist and elaborate on.
On Albion/England ruled-by-mages: cool that someone finds the idea appealing... I don't know how much I'll go into them, I guess if enough people like the idea I may focus in on them more, otherwise they might be more something distant that gets a little blurb. If I do go into them more, then I'll definitely have to answer the questions you've asked, and more.
I am really wanting to focus in a lot more on Italy, and REALLY detail a few specific cities (or maybe even mainly focus in on one initially) since I see it as being the heart of the setting to some degree, just as it gets thought of as the heart of the Renaissance.
As far as conflicts (like the Spanish planning to launch a crusade) I really REALLY want some sort of big inquisition, or crusade, or something along those lines to be boiling, and to bake some nasty politics and intrigue into things... but, that is going to take a lot more thought and time. It's also I think another thing playtesting will help with, as sometimes ideas come to me as I'm running or playing games.
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This brings me to another question, ignore the ruleset for the time being: if I were to make a book that is setting only, and then release something that would make easy to adapt to (let us say Fate, but could be something else) would it be something you would want to run or play? Obviously this would mean I'd have to have A LOT more setting material, which I plan to do in any case.
Also should this be in the play by post forum anymore? I can't move it, but if it ends up not going towards a play by post (using my system, Fate, whatever with this setting) probably doesn't belong here.