As long as there’s a distinct ceremonial magic thread: I don’t think I like the locational requirements for casting ceremonies.
A ceremony’s price can be paid with special components, congregant power, blood sacrifice power, self-mutilation, or tapping an ambient place of power. Of these options, only special components and self-mutilation do not have some kind of locational restriction to them, and blood sacrifice is the worst.
It seems like it would be very difficult for a mid-level ceremonialist to cast their mid-level spells, unless they are bringing their congregation with them into a wilderness adventure or bringing a chaotic alter along with them to generate a sinkhole of evil. Using power from blood sacrifice is particularly hard for Neutral ceremonialists who sacrificed solely normal animals to get that power (an act which does not generate corruption and is not associated with Chaos), who somehow need to get a sinkhole of evil without being Chaotic or performing a Chaotic act. (Also, who needed to visit a Chaotic altar in the first place to sacrifice them. I don’t think this is so much ‘a fine line to walk’ as it is ‘this character I describe can’t exist’.)
Special components are great, but given that it is recommended they be difficult (if not impossible) to purchase, it relies heavily on the character actually encountering the specific monster whose components can be used for the specific ceremony they want to perform. They’re the ‘you actually have the perfect materials for this’ option, and work the best as a result, but are not the most common way you’re going to perform ceremonies.
Self-mutilation is barely useful at all until reaching mid-levels. A first-level ceremonialist can use it solely to perform a first level ceremony methodically, at a high risk of a mortal wound; I think it’s very unlikely for a situation to arise where someone urgently needs this six-hour ceremony performed right now. I feel like in general, if you can wait six hours for the casting, you can wait a few days for the components.
I understand that the idea is to make ceremonialists like their place of power, but I just feel like they are too tied to it. I think I’d rather see it be something like requiring you to visit your place of power (congregation/sinkhole of evil/what have you) once a week and perform an hour-long ritual in order to collect the divine power from it. (Or not at all for sinkholes of evil, honestly, given that you already need to be in a sinkhole to perform blood sacrifice, and that the divine power expires every day, and you already get ambient power from a sinkhole…my feeling is that there’s already enough restrictions on power from sacrifice.)