Found the following way on how to customize user depended fonts for reports and forms in AX 2012 client:
(1) Open a new developer workspace
(2) Navigate in the AOT to forms, SysUserSetup, designs, design(sys), [tab:tab](sys)], right click [TabPage.Fonts] (sys) and select properties
(3) Set the property visible by default No to Yes
(4) Save and compiling you the form change.
(5) In the AX 2012 client you can now see menu file (Note: blue button top left), tools, options the fonts and set the setting there user specifically
I followed your steps as noted above. The form size font changed, but the menu size did not change.
Is there a setting that will change the menu fonts?