What I find frustrating about Puel is that, as already mentioned, he wants to play a different system, but with players unfit/unsuited to that system.
I see no problem with during training, he tries out new tactics or systems, but on match days, we predominate with a style that we are currently best with.
2 years ago, we were rock solid at the back. In fact, at the end of last season and beginning of this, Morgan was playing as well as he had done 2 years ago. Losing Huth to injury was a big blow.
Personally, I would start with 'style' changes from the front. Vardy is obviously far and away our best striker, so whatever tactical change Puel wants should be slowly introduced there, and work backwards through the midfield, with the defence the last to be asked to change.
I think trying to make the whole of the existing squad change style is a mistake. Play to their existing strengths, instead of exposing their weaknesses on match days.