Resetting when a unit dies goes against the spirit of permadeath. You obviously can still do it and lord knows I've done it tons of times over the years, but I do believe that the games were designed in such a way that you're intended to accept the consequences of death: it's why the games give you so many units and sprinkle in periodic prepromotes that can contribute immediately.

With that said, my preferred method of playing the past few games is 1 run through on casual to experience the story and all the chararacters and then subsequent ironman playthroughs on classic. If you like, you can substitute the casual run for a classic run with the turnwheel: that's what I did in Echoes and what I will likely do for 3H as well.