Check out the bluth leagues if you wanna know how to run a league, BootySweat aka Hot Fuss started them and he did a really excellent job of setting them, sure he had a few mistakes with a thing here or there, but he was very active and dedicated and it made for a well knit awesome league. NHL 14 will be much better. Its kinda late for a GMC except for a season or two in the summer.
I honestly think the sims are too far apart. The leagues im in with the most activity are the ones simming every couple of days. Everyone knows nhl 13 is ending soon so they see you may only get 1 maybe 2 at best seasons in and aren't dedicated to it. That being said, more simming means less human games. It doesn't help were starting to get into summer. I know personally i've been outta town the last 2 weekends for weddings and haven't got any games in friday - sunday.