FF,
I'm not sure if that would work. Looking at the flight director when it is in T/O mode it seems to command a nose-up pitch for the entire takeoff run. I suspect that the autopilot would command a pitch up and you would get an underspeed rotation, probably resulting in a tailstrike.
This is on the 757 btw, I'm not sure how other types work.
If you fancy giving it a try, then please do post and let me know how it went, although I suspect we would be reading about the incident in the R&N section first.
