Well I think you have two major decisions to make right now,
First of all is killarny the planet you want them to be on? You dont have to compromise your vision of the game just because they want to have a game of thrones. Even if they are some scumbag nobles. You should decide quickly if you want the challenges they face to be an external threat (dc or cc) or something else.
Second and more important is that you need to flesh out your major character and that is this planet they are on.
Well, the planet itself is rapidly becoming a character in it's own right. Since the players would like to stay focused on their homeland instead of galavanting around all creation... the focus initially will be there till which point that I do decide that they have annoyed/stepped on enough toes to warrant a proper retribution.
Threats I am developing currently are a mix of domestic (old guard loyalists to the noble's parents/status quo), corporate (not everyone operating on planet is going to like the talks of nationalization), and external (the inevitable spies from abroad/higher ups). In addition, a former player who can not make it to the games in person has volunteered to 'run' the Grand Duke that is above them... another Machiavellian individual from olden days that I play a different game with so there is some work there. This is a wild card character who may or may not be a friend or foe but the fact that he is doing this is being kept away from the players so they think it is all my planning (yay for knowing none of them come to this board).
Heavy industrial? Awesome. Thats a character, or a group of characters. The noble may own the planet. But this is the federated suns. Those businesses have leaders. Those leaders can be antagonists.
Already working on this to a degree. There is a good mix of domestic companies that operate only on planet (IE: Not the AAA interstellar megacorps) that are the current antagonists for the party at their level. As I have not nailed down yet what major interstellar corps might be on world (it is hard to pick), the players have been patient in giving me time to develop this major challenge that lays before them but knowing how the player who is playing the noble has acted in the past, he will try to collaborate as much as possible... think Rheinmetall or Krupp kind of deals. Hasn't gotten the courage yet (lacking the powerful enough base) to offer such a deal but it will come inevitably... once the local corporations have been brought into line... depending how the RP sessions play out.
The characters 'own' the planet. They do not own people and corporations have an annoying tendency to 'be people'
What about the agriculture? Who owns these farms? What are they after?
Working on that slowly... trying to map out the nobility that branches down to the lords who rule over the farming communities and how much feudalistic I want to keep it currently. Since a few of the players are farming families IRL before moving on to different careers, they do have a some experience on how major large scale farming is done. So this is being worked on and has come up as a concern of certain players.
What about the water? Is it purified by star league equipment? How is that equipment doing. That can be an antagonist.
Aquifers and minor purification of trace minerals for farming and smaller town and city needs. Some star league level equipment needed to support the 'major' coastal cities to meet demands but it is moderately good repair. This was immediately identified as a concern by the players... thus some questions determining towards how difficult to maintain and supplement with locally produced. Costs are difficult to pin down for this level of equipment.
Stop being worried about the money they make. Hell give them more money. Have the corporations try to buy them. Itdoesnt matter. The federated suns desperately needs mechs. So at best your nobles are going to spend crazy sums of money so that they can strap machine guns to agromechs.
You are right, I should stop worrying... it is kind of looking at a much bigger... problem is not the right word... puzzle or project... and picking at the closest, most obvious part of it.
The amount of money is no big deal unless you let it be an issue. Sure they can buy a lance of locusts. But that is an adventure. They have to find someone black market to get them to them. Black market locusts cost more money.
They are also piloted by dudes who arent the pcs. So if your guys are super crafty devious guys what about super crafty devious people working behind the scenes to expose them?
Your npc antagonists can be good guy hackers.
I am perfectly sure that they are going to make a good share of their own enemies. Things are just getting started to be honest. They will inevitably create a few and they already have to some degree. And a good hacker is always a good antagonist.
Now, as for the buy a billion rifles comment... that is another reason they are asking me a ton of questions... because they want to engender a sense of loyalty and pride in the population... to make them motivated so that they can actually have a motivated populace to draw upon for recruits. They know they can't get original flavor ComStar level of dedications... not from the Federated Suns... but they want better than a malaise attitude from the general populace. This... I can play with... because fanatics will always grow and with a good knowledge of history of how a certain other organization like what they have...
ITs important that your players have fun. But they can only get as much influence and power as you let them have. If thats what will make them have fun, then awesome, but if they are after power and influence make that the adventure.Make them earn it...
And tell the story you want to tell.
I am willing to give them the power they want... if they actually are able to proper earn it.
If the players arent going to do it then create some good guy nobles who are trying to do the right thing and overcome the troubles with the people. Sure your pc nobles will have to try to kill them and backstab them. But those nobles could perservere without killing the pcs. It can be a reverse adventure.
It could be crazy fun.
Oh trust me, in other campaigns... they actually have the problem of always feeling terrible about trying to deal with 'good people' because in their dealings... an honest person is so rare that they hate to kill them till they are forced to. That really is a wonderful too. They have no problem ever dealing with other corrupt people, other evil characters... they can relate to them and understand... 'noble' people are often so different and frustrating. They love having them as supporters but rarely are able to understand them. They are my favorite NPCs to create and play honestly.
But I will have to say, thank you for asking me these questions here... it lets me think and crystallize some details that tend to just be floating about in my mind and points out directions that I need to think in. I do appreciate it.
Addendum: Thanks for the direction to look towards. As a former fan of the Bannson's Raiders, I am familiar of him and I should probably refresh myself on his rise, failings, and problems. And I don't put it out of the realm of possibility that at least one of the players has machinations to someday reach that level of power or greater (namely the former Alpha Noble).