Hi Superliner...
just as a slight aside...
Just as an addition to what B737NG said, and, at least with the B737NG, those fitted with the (HUD) Head-up display(s), the runway localizer IS used for centerline guidance when doing a LVTO (low visibility takeoff), the HUD also provides a readout of the distance-to-run before the runway ends.
The height at which the autopilot can be engaged after liftoff is a regulatory issue, I believe, as the airplane will engage at any height.
But in the B737NG at least, the takeoff is controlled manually until airborne, as B737NG mentioned.
Cheers...FD...
