Tomas I am sorry you didn't get to play. I think you made a very smart move to bow out rather than possibly ruin others game. That says a lot of good things about you.
Here is how we make the core vs reg work.
Every Wednesday we have a core table and a reg pfs table scheduled. They are not the same scenario. They are not necessarily the same tier although at times it works out that they are. A third GM is scheduled as a back up GM. The back up GM may at their discretion prepare one of the scheduled scenario's, an evergreen, or a 1-5 tier that we haven't ran in the last 6 months.
We have a monthly scheduling meeting that the whole lodge is welcome to attend. We figure out what tier and what scenario's we are running for the next month (The meeting to plan November's scenario's took place Oct 13. They were posted by Oct 16) If you can't attend we welcome input via email or facebook.
We use warhorn for our sign ups. The players know that if they are waitlisted their options are to join the other scheduled game if seats are available or play whatever the back up GM has prepared. This encourages folks to sign up early so that the organizer has some idea what they are looking at in advance.
Once the scenario's are posted we don't change them. EVER!!!! We have played the "try to please everyone" game, it ends in stressed GM's & organizers and half your player base feeling as if you don't care about them because you did what the other half wanted. Is there complaining that we aren't running the right tier, campaign, storyline, ect? Yes there is, some of it legitimate and some of it because there are people who feel the need to complain regardless. We then start a dialog about what they are unhappy about, what they would like to see, and then WE ASK THEM HOW THEY WOULD LIKE TO ASSIST IN MAKING IT HAPPEN. Suddenly the legitimate ones are volunteering to GM or showing up at planning meetings. The complainers shut up which is equally beneficial.
I want to make sure that Jack Brown understands that I am not criticizing how he handled the situation. I have done the exact same wrangling trying to make tables work and at one point I ended up crying in the store's back room because I couldn't kill the players who were pissed no matter what I did. This is why I don't do it anymore.
As a lodge we recommend every new player makes both a core and an reg pfs character so that their chances of having a table to play at are maximized. We frame using an iconic as a chance to play something "different and more powerful".
Since Core came out we have had a total of 2 tables not go off because no one was willing to play at them. One was core the other was regular. For us consistency seems to be the key. Our players know what is available and what to expect. The split between core tables and reg PFS tables is even. I hope this helps.