I probably have a lot of input to certain topics, but here's a few thoughts just reading through.
Expeditions vs. Guild instancesI think this is a fantastic approach. It would be so much easier to help players across all tiers with expeditions, or just to group with others doing the same tier content as you.
Solo-group progression pathwayI remember this topic well, and something I've tried to pioneer in the past. I think it would definitely draw some more attention to the server for players who don't want to box.
Starter/Hub ZonesI think the leveling zones are good. We could perhaps add more zones to them as well to provide even more options for leveling, just to spice it up for anyone wanting to farm AA's as well. There are SO many zones in EQ (some classic ones aside from what is on THF), we might as well use them.
I think the Planes are actually very fun, but I suggested this is as solo content in the past. Could be cool to find them as 70+ zones too.
Mounts..I love collecting illusions, and so unique/special mounts would be no different.
Something different..I think this is a fun idea. Endless dungeons (maybe similar to some LDON system) could be interesting depending on reward. Same goes for doing old content... could do expeditions that scale old content up if we choose. I think choosing appropriate rewards for something like that is tricky... not all of us value the same things.
