I've been working on a game/novel setting for about a year now called Eternal Empire. The setting involves humans (and their offshoots) on another world, who, having survived your standard apocalypse scenario several millennia ago, are now enjoying a flourishing of civilization under the patronage of their Gods.

These Gods very definitely favor particular races and ethnicities, states, families, and professions to the expense of others. A few hold loose friendships and alliances with other deities, and strong rivalries with others. Ultimately, the religious and political balance has polarized between Arqualan (our eponymous Eternal Empire) and its deities, and the Hangritic states and their deities. The Gods interfere for reasons beyond mere diversion, as this world is the only remaining place in the universe that harbors mortal human life, and discovering the reasons why and exploiting that holds severe repercussions in the noncorporeal world. Said Gods (and other spirits) are, unbeknownst to the mortals, post-human, transcorporeal entities who were more or less like them once upon a time.

Likewise, the parahuman races are largely the results of ancient, technical manipulation of genes. There are 10 of these major races (Crudag, Lenje, Dreck, Dandrit, Wondoz, Sireed, Sigrech, Slees, Creel, and Drozh) with major distinguishing characteristics and home environs, some of which can breed with each other while others can't, in addition to other mortal, sapient creatures, most important of which are the beastmen (the Vol Kor'y).

In creating the setting so far, I've intentionally made race, ethnicity, and religious affiliation a vital part of the setting, so that it extends beyond mere character sheet descriptions, entailing serious social, economic, and political ramifications. Additionally, the role of (extended) family and contacts is emphasized, particularly among the Arqi, whose prestige, wealth, and power is strongly linked to their Clades. One of the things I'm thinking about is how to translate these facts from the "reality on paper" into a mechanic that affects the way people actually play their character.

The world also has a strong sense of history and tradition, and the back story stretches back about 2.5 thousand years, detailing the movements and settlements of peoples, the rise and declines of both localized societies and regional empires, and ancient enmities and kinships that have had an effect on the current world. Here again, religious beliefs and the crafting of their pantheons (almost fully developed) play a key role. Additionally, isolated enclaves around the planet have persevered, guarding the treasures and knowledge of the golden ages before the apocalypse. These enclaves form sub-societies of their own, and the liberation of their knowledge simultaneously accelerates progress and provides a living, cultural anchor to mythical antiquity.

So I'll occasionally provide notes on my progress, put up ideas, and ask for advice as it comes. But in addition to the ideas and open-ended thoughts I've supplied above, I have some general goals I would like some help with.
1. I don't want to discourage players from creating characters that are lesser deities, or half-mortal demigods, and while their powers do not strictly defy the laws of nature, their abilities and knowledge can be destabilizing. Any ideas of how to work around this?
2. I'm looking at a technical base that is both semi-futuristic and semi-anachronistic, due to incongruencies in scientific/technical knowledge as well as cultural and ideological differences. As some idea, the more avant-garde regions have electricity, internal combustion engines, refridgeration and airships, while highly elite (and divinely favored) elements have compact nuclear batteries, submarines, and personal railguns. Magical items also play a part (singular devices of advanced technology that may even be widely produced, but whose workings are not understood and have limited, novel effects). Trade is highly developed, with sophisticated institutions and commercial infrastructure and warfare is a mixture of WWI-style meatgrinder, rolling steel offenses augmented by rare (divinely-inspired) Space Marine type superhuman elites.

Ideas on this end are always welcome, as it is proving the most tenuous to execute.
3. Magic as it exists is highly risky, touch-and-go, and absolutely loathed. It entirely involves the summoning and binding of demons (a la Sorcerer). Admittedly, I'm much more of a sci-fi kinda guy than the dark fantasy type, so getting the right feeling with this is proving tricky.
4. The civilizations are comparable in many ways to those of the Classical Age of Rome, Greece, and the like. Just like in real life, I want to convey the infrequent, though stereotypical occurrences of wild excess and "decadence" of globe-girdling empires, with the far more common, entrenched conservative morality and simplistic way of living.

Thoughts?