Overall, great post Geoff.
I do have concern over renown earning and decay. I will explain why...
I've been in three guilds in the four years I've played. A small one that moved to LOTRO, a large one that died and now a small one again. By small i mean 8 people total. Right now two of those people are away for the summer. That leaves 6 players. We all have jobs and play a couple hours each, probably about 5 nights a week.
My guild (the one I belong to, as I'm not the leader) will never be level 80 or have that much stuff in the airship. That's okay. I do worry however that we won't even make it to getting, let alone maintaining, enough guild level and renown to hold down a full set of +2 stat buffs (or caster buffs or... you get the idea.) Yes, I do believe that the buffs provided on the ships are significant enough to affect gameplay and grouping.
Sure I could switch guilds. I have a standing invite to one of the largest and, in my opinion, best guilds on my server. I run with them almost every time I'm on. My little guild and theirs are good friends. But! My little guild are my friends.
Anyway... it seems to me that level 26 is pretty low to start decay, unless maybe your suggestion of permanant ammenities is made available. We could work really hard on it. Maybe even get a few other guilded friends to join and help for a while and build our ship and then we could just plug along like always.