Above and below Vtoss I can understand. But the concept of ACH applying on departure above Vtoss escapes me. The a/c is already effectively in the 'go-around' configuration and is hardly in the process of landing!
KISS would seem to apply here?
Why not just operate the a/c such that, once above Vtoss an engine failure at any stage of flight will not prove critical. Use such speeds and configurations as will enable level flight at least in the event of the failure of the most critical engine. Fly the approach (with both engines operating) in such a configuration that it may safely be continued following failure of the most critical engine (might require some demanding power, drag, trim and fancy footwork following a failure when close to Vmca in the landing configuration?) - and subsequently only configure fully for landing when at ACH on one?