Is it possible to use Shouting and Exaggerated Gestures during ceremonial casting for the cumulative +2 bonus this offers?
I was considering forcing a Stamina roll vs Ease Factor 3, +3 per 30 minutes of the casting time (so Lvl 10 spell is EF 6, Lvl 20 spell EF 9, etc) to avoid losing an additional Fatigue level and having your Voice range reduced by 1 range (e.g. Loud voice range reduced from 15 paces to 5 paces, etc) until you rest for a night.
Personally, I'd just say no. You already get the bonus from your Artes Liberales and Philosophiae scores, so missing out on that small bonus is not that big a deal. And saying that you spend all that time shouting and throwing your arms around for that long just doesn't make sense to me. Particularly since ceremonial magic is based on the principle that you've the time to think and meditate on the best way to cast the spell. Let the bold gestures and strong voice be a feature of single round casting. IMHO of course.
Using a prepared space can take casting time down to a minute per magnitude according to HoH:S - shouting and exaggerated gestures should not be a question fatiguewise in such cases. Stamina is already factored in for the casting total - and requiring a fatigue roll doubly penalize a negative stamina or doubly rewards a good score.
Shouting and exaggerating gestures over time should rather have roleplaying consequences like getting the neighbour's attention in a town or creature's/monster's attention in the wild. Magi should think twice before shouting in esoteric latin outside their own laboratories or casting room.
I am not sure if I interpret the rules right, but I do not see someone chanting for 15 minutes per maginitude. Instead I see the ceremonial casting like this:
The magus uses his knowledge of astrononmy, geometry (Artes Liberales) and knowledge of the sub-lunar world (Philosophiae) in order to prepare the casting, which takes approx 15 min per magnitude. When all this is done, the magus cast a normal spontaneous spell (takes 1 round) and during this round of casting, the magus can use a booming voice and flap his arms to get the +2 bonus
I note that "A prepared space" is kind of fuzzy. From what I remember, you don't need "a prepared space" for each spell, just for Ritual casting. How about a formulaic spell to create "a prepared space"? Doesn't need to be permanent, so it shouldn't be too high level, so fatigue shouldn't be an issue, and getting rid of "15 minutes per Magnitude" is a pearl of great price. Am I missing something?
Quite a bit. Prepared space varies and isn't as fuzzy as you remember. The formulaic spell you suggest might get it down to 12 minutes per magnitude. See page 59 of HoH:Societates for more details, but under no conditions would I let a simple formulaic spell get you down to 1 minute per magnitude. That's imply far too abusive.
 There is a situation where this could become possible, and that would be if the character had Mystical Choreography.
To be honest, I do not think that this would work. The use of Philosophiae and Artes Libearles is in my eyes used to prapare 1 specific spell-effect, at one specific time and 1 specific place for 1 specific situation.
So I would never allow the thing you described. Every effect that a ceremonial magus wish to cast is unique as it has to do with the connection to where they are, the places of the planets, sun, stars on the sky and maybe even to the ley lines and all this in conjuncture with what spontaneous spell said magus want to cast.
I would tend to agree. I believe that's why such bonuses aren't applicable to formulaic spells by default: their inflexibility prevents using that kind of tailoring to any real effect unless you've been especially trained to do so.