I doubt that any other kind will be remotely possible until Game 5. 
If the priests are the only administrative-experienced class you try to keep on board, it’ll get you further than a merchant-telone combo, but not as far as a coalition that includes the aristocracy.
Sure, but she’d already have whatever research outcomes you’d managed to help her achieve. You can’t put that back in the bottle.
If a disgruntled MC then started trying to broadcast the fact that, “She took my help and betrayed me,” the damage to Phaedra’s reputation would probably be greater from having taken an infamous rebel’s help than from betraying him. The harm to your own reputation among most rebel-supportive factions would be greater on both counts – both working with the Diadoche and trusting her.
This will be a narrative that the MC can pursue… and discover there’s no “perfect” world achievable down a road of maximum brutality either. The idea that you could avoid famine by e.g. outright butchering 50% of your population, if only compassion didn’t get in the way, is the kind of illusory solution that tempts revolutionaries and armchair social engineers into both moral and practical disaster. Even Pol Pot, with a modern tech toolkit on his side and nothing resembling compassion holding him back, didn’t get within shouting distance of that figure before his country started to collapse around him.
“Regular taxes” are the challenge here. As in most premodern and early modern states (and many less-developed states even today), most of the Hegemony’s population is never regularly or systematically taxed. The state raises most of its resources by taxing the trade of goods across borders, monopolies or excise taxes on the production of some high-value goods, and irregular taxes that mostly hit conspicuously propertied people like landowners and guilds. The Hegemony has recently been trying to increase its fiscal capacity through deployment of a dedicated branch of the state, the telones, but their focus is on turning the irregular taxation of propertied subjects into regular taxation – the idea of extending their role to taxing everybody would still be in the realm of speculative fiction in the Thaumatarchy.
A nonlethal blood tax sufficient to achieve a minimum of desirable Theurgic goals can only be achieved by significantly expanding your tax base and roping in millions of people who have never been regularly taxed before. Allowing your existing, relatively small tax base to get a write-off from the Telones for complying with the blood tax might somewhat reduce its unpopularity – but only slightly. It’s still going to be a hugely humiliating and frightening prospect for the generations who associate it with helot sacrifice.
If you spread the knowledge of Theurgy widely, I don’t think a blood tax at any but the smallest scale would be feasible. You’ll have massively boosted the potential for anti-tax revolt, while also giving people the sense that they can do most of what they need to themselves, so why should they give blood to you rather than keeping whatever they collect for local use? Maybe at that point local monopoly access to quicksilver and the other aetherial blood ingredients could become a leverage point for state formation, but on the whole I think a world where the secret of Theurgy is fully out of the bag is one that will be going through social convulsions and fragmentation for a very long time; it’s not a great context for a major leap forward in state capacity.
Similarly to the civil structure, yes – but with rather more formal levels and detail. The priest in charge of the Outer Rim would normally be selected by the Ecclesiastical Eparch of Rimmersford, but in the Olynna prologue the aristarch used his connections to the Archimandrite in Grand Shayard to shortcut that process and get a hardliner directly appointed.
Thanks, @Kevrj, for the bug catch. That’ll be fixed in the next version.
I’m not going to give precise answers to questions of Theurgic range, because it varies significantly by individual Theurge based on their level of insight, understanding, and experience. Seasoned military Theurges are much more combat-effective than Theurges who haven’t had their training and experience – but Theurgic combat is also extremely high-risk, with even the most experienced Theurges capable of being taken out quickly by surprise, so neither Hegemony nor Halassur have built up a huge body of super-Theurges.
The amount of aether you burn is proportionate to the Change you’re trying to make, so there’s also no fixed “cap” of phials per second. If you have a super-concentrated phial equivalent to 100 normal phials and you’re just levitating yourself, you’re going to waste a lot of that aether as it vanishes faster than you use it; but if you’re trying to move a mountain, you’ll burn through all that aether in a second and want more.
As for flying:
and Theurges tend to burn around 1 phial per minute in the air.
The process that generates enormous Xaos-storms isn’t one I’ll be explaining in detail until G4, but it’s not one that could be done simply with 8 years of training and a cut of the hand – nor is it one that I think will be militarily very useful. Small tactical Storms can still be horrible, especially in packed urban settings, but the damage they do is I think comparable to what a home-brew terrorist can cook up in our world. A bit more intensive research may also uncover ways to make them more mitigable than the big ones, with measures short of Great Wards.
Ultimately there are reasons the Hegemony isn’t already using Xaos-storms as weapons of conquest… and I’m not sure the destabilization of a world where everyone knows how to set people on fire using their brains will be markedly increased by the fact that people who put in 8 years of study can also hit a platoon with random, usually devastating effects that can easily backfire on the attacker.