The point I was trying to make is that there would be very little difference between a hereditary noble family and a hereditary business family, just a title.
IMTU there is an actual function for hereditary nobility. They are the head of Imperial government at each level of Imperial organization.
A Baron is responsible for overseeing the Imperial Magistrate court on his world, the Baron and his Magistrates hold only the low justice: only able to impose fines or other economic sanctions, appoints magistrates and Imperial Constables, recommends Imperial Reserve military commissions and promotions for members of the planet's armed forces who are subject to call up as Colonial Fleet or Army of the Imperium units, inspects such units and elements to verify readiness for call up, serves as commander (or an appointee or member of the Baron's household) for Colonial Fleet , Army of the Imperium and his personal Huscarl units when called into Imperial Service. Serves as operational commander in chief for immobile Imperial units assigned to the world which have no other CiC present in the system (deep meson emplacements, SDBs, fighter wings, etc) Recommends appointments to Imperial Military academies. Etc, Etc...
A Count, Viscount or Marquis performs the similar function at the County level: Oversees the County court and judges, Appoints Sheriffs and their Deputies, mediates disputes between world within his county, holds the low and middle justice: able to impose fines or confinement for violation of Imperial law within the County, serves as the court of appeal for Baronial Court oversees Imperial Confinement facilities within his county, endorses the Baron's recommendations for Imperial Reserve military appointments and appointments to military academies. Recommends individuals for knighthood. Etc, Etc...
A Subsector Duke Makes appointments and approves commissions or promotions of reserve officers, academy cadets and midshipmen for Colonial Fleet and Army of the Imperium service, serves as commander in chief of Colonial Fleet and Army of the Imperium units called into imperial service, as well as commander in chief of Subsector Fleet units. Oversees Imperial reserve personnel and mothball yards within his subsector and calls reserve personnel up and activates ships and other equipment as required in wartime for transfer to Subsector Fleet, Sector Fleet or Imperial Fleet service. He also oversees subector courts holding low, middle and high justice (anything up to the death penalty), appoints subsector court judges and Marshals, serves as the court of appeal for County Court, recommends creation and appointment of life nobility, endorses knighthoods. Etc, Etc...
A Sector Duke serves as commander in chief of the Sector Fleet, oversees the sector military academies and schools, appoints and commissions and promotes Imperial officers, cadets and midshipmen inspects and certifies local academies for equivalency and compliance with Imperial standards, oversees and appoints judges to the Sector Court of Appeal and Imperial Gendarmes, Conducts diplomacy in the name of the Emperor with polities enclosed by his Sector, recommends creation or appointment of hereditary nobility, endorses creation and appointment of life nobility.
Archdukes serve as supreme commander in chief of all Imperial military units assigned to his domain, knights citizens for service in the name of the Emperor, endorses creation and appointment of life and hereditary nobility, conducts diplomacy in the name of the Emperor, etc, etc...
Life nobles as those created for service or achievement. Their patents expire upon their death. The only hereditary nobility are those who are, or used to be, Peers holding governmental authority over demesnes... those listed above.
IMTU the nobility ARE all 3 branches of imperial government. They ONLY have power over Imperial law and government, which is actually has very limited impact on the average Imperial citizen, but within that realm their power is absolute. For example, the average Imperial Constable only has primary authority at the starport and some few other imperial reservations that may exist: a research station or something; OR when a violation of Imperial law is alleged elsewhere... claims of slavery or weapons of mass destruction somewhere on the planet. There are exceptions: one planet contracted planetary law enforcement to the Imperial Constable and his deputies long ago, several others have contracted with the Imperium for their local agencies to perform the duties of Imperial constable as well as enforcing local law.