I see where you're coming from, but an issue I see arising from that is the divine bleeding into the other realms. How do you handle someone who has genuine faith in Odin? Or in a more extreme example what if someone earnestly has faith that Lucifer is the saviour of mankind? Is this encompassed by the divine realm? If not, why, and where is the cutoff? It could work I think, but would require a complete and all-encompassing change to what the nature of religion in Mythic Europe is.
In regard to the previously discussed ideas I think it's important to point out there is a difference between the tangible power of the divine on earth as channelled through religions, and the actual true nature of the divine itself. The later part is what would be unknowable/transcendent. People see the former and draw natural conclusions from that, yes, but that doesn't mean they are right. Just like people can see faeries and magic beings exist, and naturally draw conclusion from that, but the actual true nature of faerie and magic is not something anyone in Mythic Europe can know or prove for certain - and those are realms which interact directly with people more often than the divine in many cases.
For those realms that true nature is left open ended and only suggestions are given in 5e, I think the divine would be more internally consistent given a similar treatment.
We've got a bit off track with all the divine stuff in this thread so I've made a new one for this topic: