Kevin,
I think this would be possible, but you'll have to actually hack the "c" that makes up PHP.
Each "module" of php seems to have a function called "PHP_MINFO_FUNCTION". That function generates the various entries in the page for that function.
It should be possible to remove things from the display by modifying that function.
NOTE: I have never tested/tried this. I have just dug through some of the 'c' code to see where it was pulling information from the generate the phpinfo() page.
Frank