What ideas does Washington propose to address future rebellions of the same nature in the letter to Henry Knox?

George Washington—the heralded Commander-in-Chief of the Continental Army who led colonialist forces to independence from the British Crown—wrote a letter to his friend Henry Knox about Shays' Rebellion. The insurrection was initiated by Daniel Shays, who had served as a captain in the Continental Army. The most tense incident of the rebellion occurred in Massachusetts in 1787, when Shays and his insurrectionists staged a show of force against the state militia.
The motivation for this rebellion was due to economic woes experienced by impoverished farmers and veterans in Massachusetts. The government was slow to address the post-revolution economy and reconstruction efforts, and many like Shays had grown frustrated. Fearing massive civil unrest, Washington articulated his concern about such rebellions spreading across the Union.
Washington proposed an idea to create a national government to not only quell the rebellions, but to address the grievances of the citizens in a more efficient and peaceful manner. Washington also addressed the upcoming Philadelphia Convention, which he originally did not want to attend, as he believed it would be fruitless.
However, Henry Knox convinced George Washington to attend, as Knox explained the severity of the economic situation in the former colonies. Shays' Rebellion and other radical political movements inspired by the insurrection would greatly influence the creation of federalism, which is what George Washington had proposed in his letter to Knox.
http://www.digitalhistory.uh.edu/disp_textbook.cfm?smtID=3&psid=182

https://www.ushistory.org/documents/washknox.htm