Burgundy under Philip's reign was solely focus on one thing, the improvement of the Burgundian state and to implement the first Burgundian Golden Age. Philip and more accurately Anne would finish Charles the Absolute's project of forming a proper Burgundian state and while by the end of 1492, Burgundy would complete it under the privilegium Lotharingia, it would not magically come to existence from a single privilege alone. The half-completed works of Philip the Good, and Charles the Absolute would finally be completed under Philip the Rich. The foreign policy of Philip the Rich would reflect this as the annexation of Champagne, Cleves, Nevers, and Alsace would fundamentally show a goal of connecting Burgundy and strengthening that connection geographically.
This connection geographically was already displayed during the final years of Charles the Absolute but it would be Philip the Rich that would permanently bind the two parts of Burgundy together. The establishment of the capital of Nancy as the new permanent residence of the Burgundian dukes would restart the centralization efforts of Charles the Absolute. The general estates of Burgundy, which were established by Charles the Absolute in 1475, which themselves were a successor to the general estates of the Burgundian Netherlands under Philip the Good would begin efforts to move Brussels to Nancy during the years of 1480 to 1482. Charles would refuse to move the estates to Nancy believing the power centre of Burgundy was in Brabant not in Lorraine but when Philip the Rich took over the Burgundian state he believed in equal centralization and began the process of moving the estates to Nancy. The Coudenberg which was were the estates took place began to revert back into a royal palace while a new building, the Palace of Colchis which would become the permanent residence of both the estates and the dukes of Burgundy.
Philip the Rich would begin to pursue estate reform as he wanted this new advisory body to be representing his various domains, he would conduct a census which while used mostly for tax purposes allowed Philip to reorganize his domains' representatives based on class and on population allocating specific amounts of people per domain of specific class. This proto-democratic approach would allow Philip and his heirs to use this body incredibly efficiently in strengthening their own power. This purely advisory body would allow Philip to pursue broad popular reforms within his domains, mainly the lessening of tolls going in between his various domains in order to gain popular support within the people. Philip would also aggrandize the individual estates as well, expanding the amount of delegates per individual estate but also weakening it as a whole due to the increase in amounts of people. This absolutist estate reform would most reminisce his father in law, Louis XI and his conduct with the general estates of France.
The parlament of Mechelen, while unpopular would be further strengthened under the reign of Philip the Rich, while the parlament was still stacked with loyalists to the duke, Philip would believe in competence for this parlament and due to the privilegium Burgundiae, he would gain a stronger jurisidiction over his imperial lands. This careful tightrope walking in dealing with the new judicial system that is the parlament of Malines would succeed under Philip as the crown's lawyers would appeal unpopular laws that were implemented during the times in which these domains were independent. This usage of the parlament and the usage of crown lawyers would be incredibly effective in slowly taking away privileges from these urbanized centres. Arguably the only mistake, Philip would make in the parlament was not also moving it to Nancy as it any judgements in Southern Burgundy would take precious time, fortunately it would be his successor, Henri the Fortunate that would fix this issue.
The Chambres des Coptes of Mechelen would be moved to Nancy under Philip the Rich, who would begin to reorganize the various chambres established by his predecessors, reassigning them into various cities such as Brussels, Bruges, Amsterdam, Beaune, and Arras and having them essentially act as chapters or extensions of the one in Nancy. This selectively decentralized approach to taxation would eventually lead to the implementation of direct taxes by Philip in 1483, this would be as a result of Philip forgiving various fines and special taxes or aides to his domains. Another key factor to the realization of a direct tax was the slow removal of various tolls to cross into other Burgundian domains which were already declining under Charles but under Philip they were completely removed. It would be this direct tax implementation which would contribute greatly to the Burgundian golden age and the reason why Burgundy remained throughout history incredibly rich.
The establishment of a proto-executive branch for the Burgundian state was already quite established by the time of Philip the Good but it was institutionalized by Philip the Rich. The formal ducal council of Burgundy was now firmly established led by the duke and his right hand the chancellor. Philip would assign various positions to each member of the ducal council such as councilman of defence, finance, trade, diplomacy etc. These positions while having overlapping responsibilities and overlapping subordinates would be useful to Philip as they were essentially memory aids and assistants in bringing the duke up to speed. It would be this ducal council that would also assist immensely in Burgundian legislation. The two most important domestic Burgundian achievements during this decade was the implementation and reinforcement of Burgundian roads also the construction of the Palace of Colchis.
The establishment of a permanent Burgundian capital would be the final nail to this Burgundian centralization as an already full treasury from Charles the Absolute would begin to fund the luxurious palace of Colchis. Both a mixture of French and Burgundian finance was used in order to build this magnificent palace, as Philip and Anne sneakily diverted funds away from France into Burgundy to build this palace, throughout the regency of Charles VIII almost the entirety of Burgundian-stolen French money was dedicated to building this palace and the road system that connected this palace to the rest of Burgundy. The incredible usage of late Gothic and early renaissance architecture would allow this palace to eclipse the palace of Coudenberg by the time of its completion. This palace would host the estates general, Chambre des Cortes and later the parlament. More importantly to the Burgundian state was the establishment of the massive road network that connected Burgundy together, this would be useful in the war of Lotharingia as Philip would fight on two fronts but more importantly it would allow safe and free passage through Burgundian lands which increased inter and intra trade within Burgundy itself. This increased prosperity would pay off tremendously in a massive windfall from the direct tax implemented in 1483.
The expansion of Burgundy would not slow down or even strain the Burgundian bureaucracy as Champagne, Cleves, Frisia, and Alsace were easily integrated into the absolutist capital that is Nancy. Burgundy by 1491, began to invest in maritime trading and began to build a merchant fleet rivalling the English and the Hanseatic League. The integration of the new lands would be incredibly quick as Burgundy began to invest and improve the already existing roads in Champagne and Frisia connecting them to the prosperous lands of Lorraine, Burgundy, and Artois and Brabant respectively. This new merchant fleet which was funded entirely by the Burgundian duke would be run by a royalist company: Burgundian Maritime Company which would eventually reform into the Burgundian Indies Company. The inclusion of the new estates into the general estates of Burgundy would allow Philip to make some adjustments into his domains, uniting the fractured domains of Ponthieu and Vermandois into the County of Picardy, absorbing Saint-Pol into Artois, and Burgundy would absorb Charolais and Macon. This would also make the heir defunct and only in 1489 with the birth of Henri would a new title be formed for the heir of Burgundy: Prince of Namur. Philip would grant this title to his new heir as technically all imperial rulers were princes of the empire but clearly the usage of the term prince would refer to the current duke as a king.
Interestingly, it would be Savoy who would be most affected by these administrative reforms as the future Philip II of Savoy was a practical vassal of the Burgundians and the new Savoyard ruler, Charles I was a firm Burgundian ally due to Philip's de facto regency over the young child. Philip would invest Burgundian crowns into Savoy, improving mainly infrastructure in Savoy and throughout the era of regencies of Savoy, 1472 - 1504. Philip the Rich would turn Savoy into a complete vassal as Savoy would be transformed into the duchy of Piedmont as Philip would skillfully manipulate his way into conquering parts of Savoy proper, and the Vaud region from Savoy turning it into a duchy firmly focused on Italian affairs. It would be in Philip's reign that Burgundy would claim itself to be the successor of Middle Francia, any merchant in theory could travel from the city of Nice to the city of Amsterdam without ever leaving Burgundian influence as contemporaries boasted.
These internal and administrative reforms would be in high gear throughout the years of 1492 - 1493 especially after the privilegium Lotharingia was issued. Philip the Rich would pursue a growth and centralization policy throughout the 1480s and the early 1490s. These efforts would succeed not because Philip was particularly special but because circumstances allowed a period of peace and the projects he was working on were merely finishing the ideas of his father and his predecessors. By the end of these reforms Burgundy would become the most powerful state in the Holy Roman Empire besides the emperor and even this was disputed to the amount of debt Maximilian would struggle throughout his wars and yet these achievements would be overshadowed by the Philip's foreign policy, in the war of the roses, war of Hungarian Succession, Bohemian Succession, French regency or Italian wars. At the end of the day though, there was a reason why his epithet was the Rich.