I must have missed a salient point here, perhaps.
Why would we be wanting to turn on the anti-ice half way through the takeoff sequence ? regardless of OEI/AEO considerations ?
... instead of having it selected on (regardless of where the system might permit the selection to take effect) throughout ?
.. .and if one expected to need it for some reason half way through, then surely the appropriate RTOW penalty would have been taken for the takeoff ?
in which case the original question is addressed in the ops eng sums for the degraded performance case ?
Please do ease my confusion, someone ....