The hereditary nobility, as it currently stands, doesn't act like a "nobility" should. For instance, their deaths have no consequences, most of their demands can be ignored, they are unguarded, except if the player assigns a guard to them, they do not excessively tax the yeomanry or the peasantry, don't deflower dwarven peasant damsels who catch their eye (angering their families, perhaps even inciting a revolt), don't have friends who can bail them out of nearly any situation, regardless of the law, don't try to really order or micromanage their subjects, or pull truly idiotic stunts like only a hereditary nobility is capable of.
Introducing enhanced noble dynamics would be a great and fun addition to Dwarf Fortress. It would add an enemy within the fortress, rather than an annoyance to be disposed of through convenient accident.
Suggestions:
* Every noble, upon reaching adulthood is a trained fighter of some sort, and requires armor and weapons, or arrives with weapons if coming to a new fortress;
* Every noble personally arrives with several highly trained guards, rather than relying on the "DM" to designate their own "royal guard"; in the case of nobles born in the fortress, they could recruit and train their own guard.
* If a noble is locked into some room, the guards break down the door. If the noble is drowning, the guards, who are master swimmers, jump in, and haul him out. If the ceiling should collapse, his guards pull out their picks and dig him out of the rubble. If the noble is, say, threatened by his subject dwarves, the dwarves are traitors, and turned over to the Hammerer for disposal.
* The noble gets what he wants. If he wants a room, he sends his vizier (or his guards, if the vizier is ineffective) to summon a miner to dig it out to whatever dimensions He desires. If he wants it engraved, engravers are ordered to engrave his room. If he wants a chest, he sends his servants to take one from a peasant's shop, or failing that, from a peasant's home. If he demands a bed, because he is getting tired, his guards poke the sleeping carpenter with their swords, and order a bed made, and brought to his room. If he wants a new mayor, the old mayor is put on trial for "treason", and Hammered. If the noble is drunk and thinks the goblins besieging the fort are his long-lost hunt companions, he orders the gate opened, and a royal banquet to be thrown for them.
* Instead of having lower morale or designating some random dwarf for a hammering when their demands are not met, the noble ensures their demands are met by sending their guards to, for example, hold the mayor at sword-point, beat the **** out of several masons (or the mason's guild leader), threaten the book-keeper's children, or do something else nasty (especially to highly skilled dwarves) until they get their 10 obsidian statues.
* If, for example, the peasantry is restless or seditious, the noble is from a noble family (and has relatives living elsewhere) knighted by the Dwarf-King, and can request further guards--or even soldiers from the King--serving under the noble's personal command, to encourage the peasantry to comply with their reign.
* If the noble were to die of something other than natural causes or "misadventure", then his relatives in other mountain-homes would be rather upset, and might send parties of warriors to enforce accountability for his death. If those armies were defeated, then the King might get involved, sending several armies to reduce the fortress to a flaming wreck.
* It would be interesting if the user could highlight a noble and hit (o) to (o)verthrow them. Of course, if this occured unsuccessfully, the player might face the hammerer's wrath.
* Of course, if the peasantry were to resist the armies, then that fortress could form the nucleus of a new Dwarven Kingdom, or a Dwarven Republic.