I kind of like an aggregate based, two leg series.
Not saying the NHL should do it, but for the European Champions League, like in soccer, it's a good idea.
If the NHL wanted to extend the playoff format I wouldn't mind if they had the 8th/9th place teams battle it out in a two leg series for that last spot. Might give finishing 1st in your conference a little more value as well since you'd get a beat up team.
Or you could have the 3 teams from each division automatically qualify and have 4 wild card teams play in some type of play in system/tournament to determine the final two seeds.
Extending the playoff format to include more teams probably helps franchises like Carolina who are continually stuck in no mans land and at least give their fans a taste of playoff hockey. I really don't think NHL can survive in 32 markets with half of them missing the playoffs every year as there isn't enough franchises on solid ground.
Best time to be an NHL fan was probably back when there was 21 teams. Miss the playoffs? no problem here's a Top 5 pick. Barely make the playoffs? no problem here's a Top 6-10 pick. There is no reward for being marginal these days other than some low teens pick that you hope might be good in 3 or 4 years.