Marigund may be a city, but it is a city of thousands, not millions. It's rather ridiculous to suggest that there are a few hundred people of noble birth and born in Marigund who are willing to join such an organization. It suggests that there are thousands in Marigund who are of noble birth, which suggests that Marigund is a city of millions.

If Marigund were that large, it would be BY FAR the largest city in the world. This is really not remotely realistic.

Dominus tecum

The word 'Centaur' as used typically (or singularly) refers only to the classic equine version that certain cultures have created (or encountered). The overall term is also used loosely to define all human-animal quadrupedal admixtures such as what might be seen when certain Keepers assume hybrid forms.
These hybrid non-equine forms may also be referred to by their Seulish Taxonomic terms: Vulpitaur, Equitaur, Felitaur and the like, but only in those regions where more than one specific species form might be encountered (specifically Metamor in this instance) on a somewhat regular basis.

Concerning the classic Centaur, there are considerable variants that may be referred to by respectful or derrogetory terms as defined by the culture using them.
Equitaur - Same as the standard Centaur but having a horse's head as opposed to human. Generally not found to have human-level intelligence but are sentient beyond the average horse.
Man-Sired - A more perjorative terminology referring to centaurs considerably smaller than average (standing approx 5-6 feet at their head), lacking the equine ears, with predominantly human facial/torso features and considerably less body hair on their upper body. Certain cultures also refer to them as 'Hinds' due to their smaller lower bodies resembling a deer-like physiology. Among centaur cultures these smaller, more human appearing centaurs are thought to be the results between men and centaur mares. They are often outcasts regardless.
Beast-Sired - Again, a perjorative referring to the generally accepted centaur form, or for the equi-taur variant (typcially) resulting between a classic centaur and standard horse. Where centaurs are not seen as 'natural' creatures the perjorative refers to the (perhaps inaccurate) thought that centaurs result between human (male) and mares. For obvious reasons it is not often expected that a human female can bring such a hybrid to term and survive.

Dietary needs:
Due to having very large bodies and very small mouths for keeping those bodies functional the normal centaur will be seen to eat continuously, or partaking in a more omniverous diet to supply higher protien to sustain their energy and growth requirements. The teeth of a centaur are amazingly tough structures, beyond even human norm, and grow continuously throughout their lives forcing centaurs to 'nibble' much like rodents do though the continuous intake of small food items tends to limit the need for some object to gnaw on and keep their teeth in good shape.
General diet is quite broad, consisting primarily of fruits & vegetables for the high nutritional value and greens for bulk and fiber. Centaurs in the 'wild' (if such exist) are nomadic gatherers where culturally developed centaurs cultivate huge orchards & gardens, and defend them with considerable vigilance (which lends to the commonly accepted view that centaurs are very adept warriors).

Tortional stresses:
Much like horses, centaurs that take a tumble can suffer very detrimental tortional injuries through their lower bodies and the junction between the equine scapula (shoulders/withers) is also quite vulnerable though extremely muscular. The lower spine of the upper torso has more vertebre than a human, with thicker inter-vertebral disks allowing for the amazing flexability of their upper torso.

Upper & Lower body organs:
As the upper body is given more to the muscle structure attaching it to the equine scapula there is little room in the upper body/torso for the standard array of organs. There is no heart in the upper torso, but there is a circulatory amendmant structure to increase blood pressure to the upper body & head. This could be considered analgous to the human heart and injury to it can be very debilitating if not outright fatal.
There are also rudementary lung structures that provide oxygen primarily for the head and serve as a bellows structure to fill the primary lungs of the lower body due to the small air inflow structures of the human head. (I have no idea what a centaur's facial structure would be like simply to provide enough airflow for the lower body.)
The upper body also posseses a reduced digestive system and segregated stomach that is the primary structure used in the digestion of meat, dairy, and other non-vegetable matter. The lower intestine from this intitial stomach prevents high-fat foods from entering the lower gut to prevent bloating or disruption of the lower alimentary tract.

It seems to me that any soldier or warden *when carrying out his duty* essentially outrank nobility; they are acting with limited powers granted by the Duke or by the Duke's representative (in the case of Euper, the Duke has granted law-keeping authority to the city, and through its charter it has designated the Wardens as the official instrument of that authority). This is why a Warden may arrest a nobleman accused of murder.

Also, do we want the Watch to have the ability to hold impromptu courts and mete out justice immediately? While I could see them throwing someone in the gaol for basic and blatant violations of city ordinances, as well as defending someone, how far do their powers extend? Maybe I'm misunderstanding the intent.

For non-petty theft (i.e. more than just pick-pocketing, or 'small' sums of monetary value), for assault, and frankly for most things where there is both a plaintiff and defendant I would think these things would go before a magistrate. Civil issues as well (suits, breach of contract, land disputes, etc.). Magistrates would only have limited power over nobility, unless granted authority by the County Courts.

Perhaps I'm somewhat confused on what the 'High Court' is and what it is for. In my mind the 'High Court' would be the County Courts, where trained judges preside over serious cases of murder, rape, arson, etc. County court judges, though not noble, would have jurisdiction over the nobility because they are, in effect, exercising the power of the Duke in discharging their duties and are his representatives.

The Duke's Court (where Matthias, Lynn, and others have been tried) would be for either crimes committed within the Keep, or crimes that the Duke felt were important enough they could not be resolved in a lower court, including (potentially) appeals. In Keeptowne, I imagine the Seneschal or a representative would be responsible for adjudicating petty offenses that do not rise to the level of a criminal act.

Does this make sense, and does it fly in the face of anything currently canonized out there?

Can you picture the sun rising over the walls of Metamor town (the city directly outside the variable geometry keep on the rock outcropping) drawing long lazy shadows from the Latrine Towers scattered all over the city?

How about the open wagons underneath? People sneaking in to "look up" at naked behinds? The ODOUR, even if changed daily, in a world of enhanced animal noses? The endless train of "shit wagons" going up and down the road to and from the top of the rock outcropping Metamor is on top.

The idea is LUDICROUS!

Is there no review policy on this stuff? This was put up in MAY and nobody said a word until I started ridiculing it.

Yes, some castles had "latrine towers" but they were sealed stone structures, usually over a river that the doodoo plopped down into.

Building all these towers out of STONE would be insanely expensive!

If you HAVE to have some kind of "high tech clever" waste disposal system, where does all that water pumped into the keep go? Just pipe it out of the keep, along the top of the ridge, through Roman style latrines, and then dump it off the side of the ridge and out of mind.

Though— writing the great "Latrine Rooftop Chase" has a certain appeal, as some towers are knocked over splattering goo all over the street, heavy pursuers crash through the roof an plummet down into the "well padded" wagons, the lineups at the base of people waiting to use the facilities getting bowled over by the goo falling from a wagon knocked over when a tower falls..