While I would not call such limits necessarily arbitrary, your point aside stands.
I am using arbitrary to mean more, culturally/situationally derived? The Power the US President wields vs the UK Prime minister are not laws of the universe, and are thus somewhat "arbitrary" and a product of local desires and assumptions. Arbitrary is probably too strong a word though, and may be communist post structuralist subversion in my thinking/language. There may be a better word that doesn't prejudge the situation as much.
After all, more or less all of history suggests any functional long lasting State needs some sort of Head of State where a lot of power gets concentrated into a single individual. Thus, having a head of State is not arbitrary, but seems to be some product of the way the universe works.
But, within having a head of state, there does seem to be fair bit of latitude on how exactly that head of state is set up and empowered. So, you need to have 1, maybe 2 people who are ultimately in charge, with two heads of state seeming to work in certain circumstances quite well (Roman Republic/Sparta), but that person being there for 1 year, or 10, both seem to be fairly functional. So much of these discussions is really trying to figure out what the limits of the possible is.
You for example seem to view limiting intergenerational wealth as an Ideal that might be achievable, and would be desirable, while I don't really think its achievable (your trying to work against the interest of all parents in a way that requires their buy in, which does not seem possible as a political program, long term) nor even desirable (I think having a petty aristocracy and a great many families with pots of intergenerational wealth is actually useful, and that it is better for as much wealth to be spread out in true ownership of private hands, and most conventional attempts to stop intergenerational wealth transfer involves instead concentrating wealth into impersonal ownership in the State or a corporation of some sort).
So, while we may have somewhat similar visions, we do disagree over the possible and how such a vision may be manifest.
again, though who controls and determines the limits?
The powers that be, that apply the current limits to power? I don't see how recognizing that governments and the powerful exist is some sort of gotcha.
In the US congress passes a Bill, maybe needing a constitutional amendment, though given the legality of progressive income taxes, wealth taxes like property taxes, various price control laws, I don't really see a reason such a law would be unconstitutional, but if there was something I missed you would then need a constitutional amendment.
... I don't want a liberal order. I want a libertarian one, first of all. They are similar, but also have major differences (liberalism is way to happy with wars and regulation).
And no, they don't go hand in hand. Yes, some big businesses like the big state, but I have nowhere near the problem with big businesses that I do with the state, they don't kill people nearly as often as the state does. They don't do massive thefts from everyone. They don't imprison hundreds of thousands on bullshit charges like drug crimes. And I could go on. And that's just the shit the US does, every other country is much worse.
See, imagine government as a hammer, with a lot of hands grasping at it, some with bigger hands and a more secure grip than others, all of which are trying to use it to bash each other, some working together, some working separately.
What you are proposing is just loosening a couple of the grips in favor of other grips which are just as strong, if not stronger, in exchange for making the hammer bigger, when it's already 100 times bigger than it needs to be. Those hands with the now firmer grip would be the companies that aren't hit because they don't have major owners (like every military industrial company) and the deep state. Every communist ever promised that the hands that got a better grip would be 'the peoples', but in reality, it was only ever a new set of higher ups, more powerful than the previous, as they were directly hooked into the halls of power.
So yeah, to hell with the creeping communism you propose. Because it never stops, and will roll down until everyone is banned from being 'rich', i.e. having 2 whole meals a day.
That analogy is doing a lot of work for you, and I don't agree it accurately represents the actual structure of things. Government is not an inaminante tool random individuals control, its closer to an influence network. Trump was the President of the United States, but clearly did not operate as a man with a hammer. Government is much more a playing field to encourage the powerful to work together in productive ways, to complete in minimally destructive ways, and provide some protection that only "acceptable" people are playing the game.
At the scale this law is concerned with, Government is the board the rich and powerful play on, with this being an attempt to somewhat modify the game being played.
You also sidestepped the initial question: does the Libertarian order make sense with an absolute dictator managing the state, or does the Libertarian vision require some manner of decentralization of power, imposed somewhat arbitrarily by the definition I'm using?