I just noticed that Larry Pina does, at least for something very similar (separate, not composite video). See Macintosh Repair and Upgrade Secrets, First Edition 1990 page 169 for the 128K to Mac Plus and page 297 for the SE and SE/30. The circuit probably can be further improved by non-inverting buffering the vertical sync also to give some ESD protection to the external monitor connection. The scheme is just a hex schmitt trigger inverter buffer (74LS14) that inverts and buffers specific video and horizontal sync signals, passes thru a vertical sync signal and leaves it up to the external monitor to do what it will with the pixel timing. I suspect the very older manually tunable monitors could cope with these scan rates but the newer multisync ones probably are optimized narrowly around specific standard modern timing specs.
Additional info: If you happen to have a widely tunable monitor or projector that accepts only true composite video on a single line input, see the following for some combiner ideas.
Here is a way to go from TTL levels of sync to a composite sync
http://www.tkk.fi/Misc/Electronics/circuits/vga2rgbs.html
Here is a crude sync and video combiner:
http://www.repairfaq.org/sam/vidconv.htm#nvcvgtc1
This combiner could be buffered with a video opamp configured as a signal adder to drive longer and terminated video cables to your monitor of choice.
None of these address the pixel rate and line scan timing mismatch problems that cause distorted and non-centered renderings.