I've been thinking about the same problem in a slightly different way. The 68000 macs' graphics interface is a simple framebuffer. I have been toying with attaching to the 68000 processor (or in the SE, use the PDS slot) and just snooping the bus for writes to the framebuffer, passively keeping a duplicate copy. Then you can do anything with it. My initial thought is to just build a USB device where a host can then access the framebuffer contents as a window on your computer. Coupled with a raspberry pi or similar, you've got compact mac -> hdmi. Or, throw some GPIOs on that adapter and plug it into the keyboard/mouse port and you've got your mac entirely in a window on your computer. Better than any emulator!

This way there's zero loss in signal quality, it's digital all the way through to the final output.