Air NZ policy is V2. If ATC are forecasting a microburst situation, V2 is set per performance manual speeds - i.e. Normal V2, but VR is set to the performance limited GW rotation speed, not to exceed actual GW VR + 20. The answer to your question is still V2 on the MCP.
But who would take-off if there was a microburst warning? Not me, dude
