Madison's reasons for supporting a republican form of government are that It would give the individual states more power to better serve their own citizens.
Explanation:
James Madison proposed a change under the name of "The Virginia Plan" it was based on the Philadelphia Convention and it mainly focused on the creation of a new and more functional way of government which was intended to improve the citizens' life in every state. His proposal was supported by the writings " Ancient and MOdern Confederations" and "Vices of the political system of the United States".