Here are my initial design ideas for you guys to check out! I will post any others I come up with as well, but feel free to comment on these in the meantime...
#4 & #5: I thought it would be cool and fitting for your logo mark to be a stamp of sorts. Like an official emblem or seal.
#6: is a more rounded version, which is just as versatile and would look great anywhere. I also added a couple versions with some grunge texture over the top: #7 & #8. This gives a cool vintage look/feel for the logo, as well as for anything else you might do (biz cards, flyers, signage, shirts, etc.)
Also, all of these are strictly solid colors are only 3-color designs. Simpler, cleaner & fresher all at once! While still having some resonance of your previous look, without being as dated.
And then I also came up with a cleaner, simpler design. I think this would lend itself to silkscreening onto shirts much better than a skyline design. Plus, it's cooler and something that someone is more likely to rock on a tee! Just my opinion of course ;) #20, #21