Could we do something like "your top two lines cannot exceed a combined total of X% wanted ice time"?

I don't want to penalize teams who've worked to have depth for bringing on and calling up active players who've just come out of juniors since it will take so long for them to matter, statistically. That said, I don't really want to punish teams who are fielding a roster, period, by inactive signings and chewing gum either, but the buck has to stop somewhere, and it's discouraging to the other teams if a very thin roster with a few stars at the top are beating a team with more actives, more balance, and better depth.

If it's a combo of the top two lines, then yes, you can still have a Minnesota, and yes, you can still have a Manhattan, but it means they're forced to sacrifice some performance out of their next-best line if they choose to play their ice time that way.