Thoughts ..
The basis of Flash Gordon: Three humans become embroiled in a large scale war of succession on planet Mongo. The realms and individuals live a in a highly feudal, highly advanced, but an merciless overload has arisen to control this populace using fear, terror and more technology. One realm stands in rebellion, the humans side with this cause due to their spirit of freedom. 80 years of comics, spin-offs, series, movies proceed in telling this, retailing this, continuing this. Even now Ming sometimes is in power, and sometimes the good guys are in charge, it goes back and forth. They’ve gone on to explore the Universe, returned to Earth, defended Earth from Ming, returned to Mongo and mostly stay embroiled in Mongo politics (or feudalism).
Key Elements (should be part of any Mu* based on Flash Gordon):
Atomic Age Technology: Ray guns, thought projectors, robotics, tractor sleds, sky sleds, frictionless monorails, atomics and radium are primary sources of energy.
Action: Each panel is literally the conclusion of last weeks action with a slight break then the next threat emerges in the final panels, rinse repeat. This is centered around the conflict between Ming/Ming Loyalists and Rebels mostly, sometimes Ming is exchanged for Alien threat de jour. This ranges from rescuing allies, fighting off infiltrators, being attacked by troops, running from threats, escaping some trap or another, and facing the savage world of scary monsters and plants and environments between all the beautiful high tech cities.
Feudalism: There is a large focus on the kings and queens and disputes. From personal vendetta to the battle of heroes (ie when two troops meet, its expected the big heavies will have a personal fight at some point before or during the battle) it is the necessity for the action itself.
Exotics: From various races to plants to the background, its not just flat plans, bland streets.
What I think would work as a basis for the theme:
It is Pre-Flash era on the planet Mongo. Ming is a tyrant, and either he took over Mongo from beyond, or rose to power from within. Not so important as he controls the planet. It is a rogue planet floating through space, most of the exotics are just various species and amusements he has picked up along the way. Some of the cultures thrive and flourish, and have done so for who knows how long, enough to be established culturally in their own realms/kingdoms. Others are primitive and stay that way Ape Men, Shark Men, Dwarves, Giants. The various dragons and beasts were curiosities but helps keep the people focused in cities for control, but also makes the more nomadic/primitive people tougher for surviving these hostilities.
The focus of play:
Players are the active agents of either Loyalists or Rebellion. They actively take on missions against the other side with a wide range of objects (hit targets/locations, sabotage, disrupt society, kidnap/hostage/rescue, raid, attack locations or groups, take prisoners, gather intel). Routinely this involves traveling through primitive lands, stealthly, using survival skills and dealing with the ‘natural’ threats of the planet. Being close to the heels of each other and chasing or giving chase through these exotic locals is part of these missions, from chases or dog fights in air sleds, to dealing with dinosaur like predators in intriguing forests. Atomic Sci Fi (Mad Science) is a part of this, from disrupting power sources, to new devices to divert attention or dismantle tech threats to simply increasing efficiency in the realms themselves.
Area of play:
I think, and this may be too ambitious (the focus might be as well), the five or six major realms should be open and allow for Loyalists/Rebels to join in. They can participate in local politics and swaying their region more towards rebellion or Ming, all while serving as agents for the totality of the Rebellion, maybe led by Prince Barin, or Ming and his allies and conducting missions as noted in the focus of play. Just the exotics of each location offers various appeal to various players and each comes with its own set of unique challenges as well as different backdrops for the potential missions and adventures the players can have within the focus of play.
That’s me, I could be off if that would garner interest from others, I could be missing points to ponder. But settling focus/area would be a good lead into the areas and developing them beyond the comics or movies even, a lot of that dependent on establishing a canon.