I half wonder if any of the Parabolan powers would be amenable. I doubt either Irem, the Tomb Colonies or the Fathomking are in, but who knows…
Edit: if you complete all six call to arms, you get a fancy title. Meaning I doubt any is locked behind Fate content at least.
Edit 2: the Khanate, Godfall and Polythreme have been confirmed on top of the other two, leaving one.
Edit 3: last one is Gaider’s Mourn. Various requirements all around, only two seem to ask for Favours.
I’m kind of sad I can’t get a new fancy title. Marigold is just too far away.
Only question I have left is: what’s the time limit on this? Will I have to get caffeine poisoning to get the fancy title?
Well you really only need one long zee voyage for most of them if you plan your route well, then as long as you can get a docks favor you can get the dockers when you are back in London then it’s just a short train ride to Marigold, as long as you have a hell favor.
Do you need access to Khan’s Heart for the Khanate or just dock there?
You apparently don’t need a Safe Conduct, for what it’s worth. Haven’t been there myself yet, I’m still waiting on the Hell Opportunity Card while building up my actions for a Zee trip, but that’s what I’ve seen mentioned.
Edit: you do need Respectable 10 for that no matter what. And Dreaded 2 for the Mourn.
Don’t forget Bizarre 5 for Godfall!
Note that if you don’t have high Renown: Hell, the option at Marigold costs more Hell Favours - I only have 5 Renown and for me it costs 2.
Khanate also requires Airag, which is going to be a pain. Good thing I had the Handmaiden infiltration set up.
Interesting… my railway is all but completed except for Marigold station, which I had postponed indefinitely because I can’t decide who to sacrifice.
Perhaps now it is time to build it. I have the materials…
I think you can trade in Service to London for Airags. I did it a few times.
Time to spend some Service I guess. Thanks for the tip!
Polythreme needs Airag if you don’t have Heart’s Desire
EDIT: also, I don’t know where the Khanate needs airag thing came up, it does not.
The only time I can remember that I actually need a Docks favor, and the RNG can’t be bothered to help me out. 
Don’t forget about Favourable Circumstances (and Poetic First Drafts).
So, to recap, the six places to visit are, in no particular order:
Khanate
Polythreme
Marigold Station
Docks
Godfall
Gaider’s Mourn
I just built Marigold Station, (RIP Furnace 
), bumped up my Zeefaring to 5 to unlock Gaider’s Mourn. So I guess I’m all set.
I have a lot of favours, I love stockpiling favours for conflict cards to appear. Then use some of the favours now and then so they don’t exceed 7/7.
Just remember, Furnace isn’t dead, she’s just different now! And better a friend gone than A Brilliant Future. I play for White, but we don’t need that sort of supervision.
Aaaaand now I’m stuck with the Boatman because I rushed getting back to London. And because I keep failing 90+% checks.
Look alive everyone! We have a new reward! Just claim it from the new storylet with a dirigible icon “A Load of Hot Air” and…GASP! Could it be? What we’ve all been waiting for? An option to spend services to London that unlocks a unique item! Available now under the station IX storylet after claiming your new free affiliation.
EDIT: also, I think I’ve found the new permanent activity, and no spoilers, but it is amazing.
Keep getting new Service cash-out options but I’m still waiting for one that’s just straight up scrip gain with no extras tacked on.