I'd actually say that the Catholic model is a pretty decent model to work on as well, all things being in a vacuum. I'm sure it's not exactly the same, but we've got nothing else to go on save that they use primarily Catholic titles. As far as having bishops being sent into foreign space, that's not without precedent historically either. There are dioceses pretty much everywhere in the world, even places that are not predominantly Catholic. Since they aren't namely political entities, they don't really have a legal claim, but there is, for instance, a Metropolitan Archbishop of Tehran. Just because the Amarr don't namely own the space doesn't mean they can't send a bishop. Statistically, how many citizens live in hisec? Trillions? The U.S., with a population of 313 million, has 11,000 registered, practicing Zoroastrians. They are .004% of the population. That would mean even if the entire cluster was just a trillion people, and if that cluster only had as many people practicing the Amarrian faith as there are American Zoroastrians, there would still be four billion people practicing the Amarrian religion. Considering how much space they control, I suppose it's hard to imagine that their religious ideas haven't leaked out at all. It's just a matter of statistical scale.
It's not a new idea, but as the reaction from the community shows, it's definitely not something people are used to. Constantin's bottom-up approach seems fairly new, though, which is why that non-entity in Caldari space ministry thing is probably true to some degree or another (it doesn't matter to me how much people attribute his work to them or to Caldari businessmen, since Constantin is never very specific about it).
I've related Constantin to the Theology Council specifically because I didn't think they'd let him go out there and pull a Martin Luther in foreign space. To be fair, you can assume it isn't a universally popular position, but it doesn't seem like it's anathema to all Amarrians, just the more old-school conquering type. Plenty of people want to just conquer foreign space and MAKE them Amarrian, but that's proved to not essentially work in converting them for the glory of God. Constantin is an evangelical that doesn't particularly buy into the idea of warfare leading to conversion. Obviously, the Minmatar were conquered, and they weren't converted. Essentially, he was sent out into foreign space without much besides a stipend and a couple of staff without a lot of good examples to draw on. He's improvised ever since.
[spoiler]The idea is that the Theology Council is VERY divided about how he's done it. His ideas aren't universally loved, but they've proven effective even on the IGS at softening some of the vitriol people have for the religion. He's also had to improvise using his position and what abilities he has. The Theology Council has too many conflicting officials that can't decide whether Constantin's method is a courageous and powerful way to continue the Reclaiming without warfare or a giant misstep that is producing believers who aren't necessarily loyal to the crown. They've had the effect of cancelling each other out so far, keeping Constantin at his present rank but without recalling or replacing him. So Constantin is simply carrying on with his mandate as it stands, doing what he can to promote the religion outside his space.
It's really not as much about what he's doing in other space as much as how people react to him. He's very obviously a multiculturalist and an evangelical, so he has a lot of play that keeps him from being an easily pinned-down UAD type. People from every background and empire have good reasons to love or hate him, or even to have completely conflicted reactions to him. That's sort of the point.[/spoiler]
I do all this research and work not to make characters who are perfectly adherent to every detail, but so that my characters can't be defined in a few words and dismissed. If it was possible to say that all people of such-and-such background are then obviously such-and-such, the playing field becomes flat and characters become less idiosyncratic and much less stimulating. I am trying to cover as many details as I can and to not throw up too much of a wake, but that isn't really the point of RP to me. RP is meant to be about making new and interesting characters, especially those who aren't lost in a sea of their race, their culture, or even people doing the exact same job as they are. RP shouldn't be about chess pieces and worrying specifically about how they move. It's about group writing and being interesting.
Really, I go over the minutiae, over and over, simply because in games like this I absolutely have to or we'll all get bogged down in these kinds of arguments and forget about the important stuff. Arguing lore isn't really a lot of fun. Having a character that I have fun reacting with and that people have fun reacting to one way or another is the reason I like roleplaying. It's creative writing at its most entertaining. If shifting details makes it fit for you, then anyone can consider the minutiae however they'd like. The important part isn't about what his title is. Truth be told, that's how I know how well I've been doing at the RP bit.
Does a character bring out subtleties in other characters that make them stand out from each other? I hope Constantin does, because that's what I aim for as an artist in this obscure little genre.