The laser trial at heathrow showed that under some circumstances vortex will CLIMB. One can no longer assume they are going to descend.
There is real danger in the using higher climb gradients in order to cheat on the spacing. Imagine he has an engine failure as he rotates; he will then be slow, with no spare power and so the authority of his control surfaces will be limited at a time when he would need maximum if he gets into vortex.
I restate my previous point: Vake vortex is a killer and we mess with it at our peril. If there is a capacity problem at airports which is pushing us into this mode of ops. then we need to address that, not cut corners on safety.