That period above is the same as that for my introduction of Captn. (eventually Admiral) Johannes Wilhelm and the Austrian(?) Luftshiffengel "inter-gender" character (who incidentally still has no name).
Drafting an origin story is a daunting process. To be honest I shied away from creating a plot from the get go, because 1) I never have time to sit down and write for hours on end, and 2) I feel like I'm jumping into a void when I dive into writing, and I'm going to force my characters through impossible plot lines that I will have to dis-entangle later on.
Instead, I'm very much taking the back door approach, used by JRR Tolkien, where I create the universe around the characters first, without any time table or pressure for me to develop a plot, and the actual plot will eventually and necessarily develop from that universe as it "unfolds." That is, the main characters are just following the sequence of events.
Frankly, right now I'm just concentrating on the alternate historical background that fit my interests first, namely the Mexican Maximilian Period which overlaps with the US Civil War Period. My penchant for amateur history is doing all the heavy lifting for me right now. This approach also helps me keep all the historical details straight, and the plot just "drops" from the possibilities in the timeline.
So far I have populated my universe with two main characters who start from opposing sides and eventually find themselves in the same place, but as I developed the back story I could find the "excuse" to develop the characters and their story.
Admiral Wilhelm's origin story follows his immigration from Germany, possibly as a child, and involves military service on the side of the US Union (US) after Cesession from the Southern States and the start of hostilities (Civil War) as we all know it. The character has strong engineering and science aptitudes, but his sense of adventure gets the better of him during his youth. Eventually he'd become a high ranking Science Officer serving the US Armed Forces.
Closer toward the real history end of the Civil War proper, the turn of the alternate timeline happens during a failed assassination attempt on President Lincoln after secret agents sent by President-in-exile Benito Juarez alert the Americans of the plot, which was arranged by Emperor Maximilian during a Mexican diplomatic visit.
As it happened in real history, Emperor Maximilian is an Austrian Hapsburg prince who was offered the Mexican crown by Napoleon III from France and was accepted by the Mexican nobility, as having a legitimate claim of the crown by way of the 1500's inheritance from Charles V and Philip II when the Spain with the New Spain and the Austrian Empire were joined (again this is all real history).
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So you set the stage for the second character to come in. The so far unnamed Lufschiffengel, was an Austrian engineering crew serving on a CS/Austrian airship (eventually the CSAA Alamo), and zirs* presence on the airship is the result of a diaspora of "Engelfolk," or "Angel People" who mostly come from Southern Germany and Austria and Switzerland (thank you for the latter Mr. Atterton), namely regions with a significant Catholic presence.
The Engelfolk are a "third gender" or "inter-gender" people, who I presume to be traditionally incorporated to the region's Germanic society since antiquity (fictitious plot). For literary purposes, I envision these Engelfolk to vaguely resemble elves in fantasy stories, except that these are real human beings instead of fantastical creatures.
These Engelfolk are tolerated by the Catholic Church on condition of life-long celibacy and separation from "sexed people." But when the Northern German States, and Prussia, who are predominantly protestant, start to have a greater influence in the politics of the various German Republics (several incarnations of it - this is real life history), then these Engelfolk become persecuted by Lutheran politicians (adaptation of real life history into a fictitious plot).
This persecution results in a diaspora for the Engelfolk, but naturally there is an escape route for these people (I need to re-read real world history related to diaspora in other time periods).
Having the unusual combination of being acclimated to cold thin-air environments, as well as having a low fear of heights, and also having stereotypically female attributes, such as finesse, light weight, flexibility, and multitasking, and combining with males attributes, such as strength, mental focus, and tolerance for pain, these "Angel People" become a valued sought-after type of crew. This means that many Engelfolk end up in the service of Airship forces throughout Europe, and typically end up in engineering and maintenance positions.
Their role in aeronautical engineering eventually will lead these Engelfolk to be known as "Airship Angels" or Luftschiffengel. With the passing of time, the Luftschiffengel will form a global secret society dedicated to the their own protection as well as the development of the aeronautical sciences, which will be known as the "Angel Guild," or simply "The Guild." (For those of you who know what I'm talking about, do you see what I'm doing here? I'm setting myself up for the far future

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In the meantime, the failed Lincoln assassination attempt results in an expansion of the war into Mexico. France and Austria ally with the Confederate States (CS), into an "Axis," effectively turning the tide of the war in the favour of the CS side.
The tide is turned mainly through the use of massive Austrian airship fleets over the Confederate territory and the unincorporated territories of the American West, and also by way of French ground troops massing along the US Mexico border. The Mexican Empire led by Emperor Maximilian (former Prince of Austria - same as in real life), have been promised the return of vast areas of the American Southwest back to Mexico in exchange for Austria's help in turning the war in favour of the Confederate States who were already desperately weak.
Abraham Lincoln, of course, is obliged to declare war against Mexico, Austria and France. The British started the US Civil War by declaring neutrality as the Prime Minister, Lord Palmerston was somewhat sympathetic to the Confederate cause. However, seeing as France was in the mood to acquire territory, and in light of the Austrian and Confederate alliance, rather than help, a French invasion of the South could simply potentially steal away valuable cotton markets away from Britain.
At that point Lord Palmerston is "strong armed" in secret, and the British resolve to keep the French out of North America, thus breaking away from neutrality and ally with the Union (US); thereafter, the fight washes down to Mexico, by way of multiple "Pincer maneuvers" performed from both combatant sides, and which take US/UK and Austria/CS air fleets into the Sonora Desert, and possibly further south (I have not decided how ugly the war is going to get). So you now have a potential Mini World War.
And this is how our Luftchiffengel character ends up serving aboard the CSAA Alamo, and Austrian/Confederate airship, which according to my earliest notes several years ago (2009?) is a high altitude vessel capable of climbing to the lower Stratosphere (a goal that is quite achievable and being sought after in the real world today with certain technological advances).
Now, at this point, during a battle over the Sonora Desert the young Capt. Wilhelm commandeers the CSAA Alamo, and along with it we have a Lufschiffengel crew. The idea is to have the Austrian Engels be imprisoned and eventually offered freedom on condition of service aboard the captured Alamo, now re-christened the USAS Orca, which would survive the Franco American War into the Reconstruction Period and beyond. It is rather convenient that Captain Wilhelm also speaks German. You can at this point start making vague associations between The Angel Guild and the US Military.

See how the plot develops naturally?
The USAS Orca and Admiral Wilhelm concept dates as far back as 2009, I believe (duh! I should have known. It's my own avatar here). The CSAA Alamo re-christened into the USAS Orca is something I thought of in 2010 (
http://brassgoggles.co.uk/forum/index.php/topic,3455.675.html) The fictitious Franco American Aerial must have developed the same year after I started ranting about Emperor Maximilian and the French Intervention in Mexico... And the Luftschiffengel thing can't be older than July 2014 when an outfit idea at the Queer Geer (page 73) was turned into a concept (thanks to Mr. Vagabond Gentleman for those discussions), and right about the time Mme. Ratchet first introduced herself to the forum...
So you can see I'm in no hurry

But I confess I have to start pulling it together soon.