Personaly, I think Nelson also played this card due to the very fact that who in the hell would have the audacity to charge a formed line of battle head on. Considering the odds of this working and the coming storm this was the most decisive, quick outcome he could plan for.
He placed himself in the fore to drive on his crews, for a very good reason, lets just get it over and done with, forming two parallel battle lines only ends in a draw, and that would just drag out the issue and cost more ships and lives needlessly. I think that trying to plan a major battle when dealing with old intelligence, unpredictable seas and weather, plus individual Squadron commanders would be a nightmare...........that along with a signal system that depends on LOS I think the plan was the best one he could come up with