A very interesting question. Of course land reform was and still is a central topic in Mexican politics, and the implications of the question are far-reaching. In a first step I'll focus on developments and colonial writers related to land tenure and governance before the 18th century, and then turn to precursors of reform in the 18th and early 19th century.

Post-conquest (15th/16th c.):

Following the Spanish conquest of Mexico, the traditional systems of land tenure were for the most part abolished in favor of the encomienda-system. It was a dependency system going back to the Roman empire and transposed to the Spanish overseas possessions. At first the conquistadors, and in the following other great land owners were given rights to the labor of the indigenous population of (sometimes huge) territories. In turn for their „protection“ the laborers owed tributes to their encomenderos. In the long term it was replaced by the repartamiento-system which helped foster low-paid or unpaid work, but continued to exist formally until 1791.
The encomienda-system was closely tied to the colonial practice of rewarding achievements with privileges through the “relaciones de méritos”, used by the colonial bureaucracy to award positions and determine their inheritability. While in theory every person who took or had taken part in the conquest, mission or administration was eligible, the legal procedure to attain privileges was so complicated that only a small minority was able follow the regulations successfully. Usually encomiendas, bureaucratic posts and the inheritability of privileges were at stake (one famous example is the vast hereditary Marquisate of the Valley of Oaxaca, granted first to Hernán Cortés). The Spanish rulers tried to counteract this process by appointing Spanish men without connection to the Americas to central administrative and political positions, in order to prevent the rise of an independent colonial elite. Nonetheless, the granting of privileges (to land and tribute) through the Consejo de Indias had a central place in colonial Novohispanic society.
The relaciones de méritos were supposedly autobiographical writings showcasing the achievements of the applicant or his forebears. A petition containing a list of witnesses had to be submitted to the royal audiencias (appellate courts), from where they were passed on to judges, the Council of the Indies, and the ultimate authority of the king. Robert Folger argues that the writing of these relaciones contained tactical elements, attempting to portray a complete narrative by writing over gaps in the source material. While in theory every person who took or had taken part in the conquest, mission or administration was eligible, the legal procedure to attain privileges was so complicated that only a small minority was able follow the regulations successfully.

The post-conquest elite of conquistadors' successors lost influence and privileges through the policy of bringing Spanish-born people (españoles) into high positions, who continued holding the grand majority of the highest posts (including most Viceroys of New Spain) throughout the colonial period. Nonetheless, noblemen of indigenous descent, closely tied to the pre-conquest royal houses, continued to play an important role, especially in the administration of indigenous communities. Members of this new elite used their judicial and linguistic knowledge to defend their privileges and status – the majority of these chroniclers was related to the royal lineages of the Mexica, Acolhua and Tlaxcaltec. Many tried to create family trees legitimizing their lineage's claims to lands and properties, owing to the lack of a central (Mexica-Aztec) authority that had enforced an official version of the past before the conquest. These writings were connected to the relaciones de méritos.
Thus the well-known mestizo (of mixed Spanish and native descent) author Diego Muñoz Camargo took his writings exhalting his Tlaxcaltec ancestors to the royal court in Madrid, and was granted rights to parts of the ancestral lands he requested (note: terms such as mestizo and españoles were used in the colonial casta-system, but are still in use in current literature). Similarly, another mestizo writer, Fernando de Alva Ixtlilxochitl, descendant of the Acolhua, retained rights to a local community that were contested various times by viceregal authorities, and thus stayed in his family. In his Historía de la nación chichimeca Alva Ixtlilxochitl also goes to great pains to list traditional territories of his ancestors as well as their acknowledgement through Cortés. We can notice in these authors of indigenous descent the use of tactical writing and judicial prowess to retain at least parts of Aztec territories in their families, in connection with the pre-hispanic territorial, political and cultural organisation into altepetl („city states“). Furthermore, not only elites but also indigenous commoners used local wills and land tenure titles called Títulos primordiales that were accepted by colonial courts as a way of authenticating a community's rights to its traditional territories. The titles were used (and sometimes forged) up until the 18th century. In 1590 the Juzgado de Indios was founded, where indigenous communities processed over properties.

From 1570 onwards, the indigenous demographic crisis led to immense losses of privileges for natives. The cumulative effects of epidemics, marriages with Spaniards, the continuing European immigration, and the collapse of the ancient dependencies accelerated the decline of the traditional elites, on whom the colonial authorities did not depend anymore. Their place was taken by españoles, but also increasingly by a creole elite (born in the Americas but of European descent). These political and demographic shifts taking place well into the 16th century also led to the further consolidation of large estates, as large territories formerly inhabited by indigenous people were deserted, and the land titles appropriated by Spanish (or Spanish-born) elites.