It's relatively straightforward to do what you propose. For some details, see http://68kmla.org/files/classicmac2.pdf
Interfacing to an old TTL monitor requires just two signal inversions, and possibly a minor tweak to sweep speeds. Newer multisync monitors may need even less work.
Interfacing to an old TTL monitor requires just two signal inversions, and possibly a minor tweak to sweep speeds. Newer multisync monitors may need even less work.