Pardon? 
Do you think we could perhaps go over this hypothetical again, because I think we may be losing each other.
You asked what I would do if half the population of the country, the assumption being that they are of sound body and mind, refused to work. I replied that I would do nothing at all; they have every right to refuse to work. As long as they don't expect the rest of society to indulge them in some sort of self-appointed aristocracy, which be exploitative, then it is their choice, and their choice alone. I am not an authoritarian.
Why, exactly, is this the Stalinist atrocity that you seem to believe it is?
Systems of a society can be categorised by whether they have, and the nature of, a central authority, as follows:
1. No central authority and no Marxist abundance. As you've agreed, a dictatorship can be constructed from scratch. Where a central authority does not exist, people who want power find ways to acquire it, so an anarchy quickly develops into a Somalian style warlords civil war. This was the norm for existed anarchies that lived long enough (i.e. longer than Anarchist Catalonia) to see through the transition.
2. No central authority and has Marxist abundance. Because of abundance, supposedly nobody would want power, so everyone could live together happily ever after. This is the Marxist utopia, or the "people are all saints" scenario.
3. Central authority without limits to governmental power, of which are:
3.1. "Dictatorship of the proletariat". The ruling class is supposedly almost everyone (the proletariat). This government has all the features of a central authority, but since the ruling class is not supposed to harm itself, Marx didn't think it necessary to limit its power. The problem is that the proletariat didn't get to dictate, the Vanguard Party did.
3.2. Other forms of dictatorship. This is the norm for existed authoritarian governments other than Stalinists, from slavery to feudal to corporatist. Typically the ruling class claims that it's the elite, better than the rest of the population, so its ruling is better than mob rule. The argument is very similar to Leninism, except that Leninists argue the Vanguard Party actually represented 99% of the population (it didn't), and hence better than old autocracies where the ruling class was 1% of the population.
4. Central authority with limits to governmental power, or liberal democracy.
Unless you can find a new category, your democratic socialism must fall into one of the above. Now, it's ok to argue that your socialism takes a few steps. But it's not ok to suggest a feature of one system solves a problem in a different system. So, when you have a system that deals with "arseholes" "however you can", you can't use a reason like "fully realised system of libertarian socialism simply wouldn't be capable of supporting a centralised dictatorship", because you do have a centralised dictatorship at that moment.
Now, on one hand, your answer to lazy people is that you won't do anything, implying you don't need a central authority. On the other hand, you did say you need a central authority to deal with "arseholes". When I questioned you on that you admitted that you "don't have these things carved in stone". This ambiguity is lethal. Gradually or overnight, at any point in the transition to your ideal society, particularly in the ideal itself, either you have a central authority, or you don't. You cannot have it and don't have it at the same time. If you allow for that possibility, it's very likely you'd get Leninism again, which is the only system that claims to be a direct democracy and a dictatorship simultaneously. That is why I said your system ends up as Stalinist.
To argue that your system won't be Leninist, you need to, for each phase in your transition:
a) if the phase is of category 1) above, demonstrate why it won't devolve into Somalia;
b) if the phase is 2), demonstrate how abundance is to be achieved, or if you can offer any other ways to magically turn people into saints;
c) if the phase is 3), demonstrate why it won't turn into authoritarian.
You cannot:
i) solve a) by saying you have a central authority to handle "arseholes";
ii) solve c) by saying you don't have a central authority.
These question pertains to the idea of public welfare itself, not to Libertarian Socialism in particular. I'm not sure why you felt it was necessary to address it towards me, and not, say, Clement Atlee.
Noting that welfare governments spend a large amount of resources to simply identify who deserve welfare, you need to answer whether you also need a central authority for the same task. If you have no central authority at all, who is to stop me from claiming I'm disabled, and taking whatever I want without working for it?
Also it's worth saying that modern capitalist welfare err on side of spending more, so it tolerates some people "who are fully capable of contributing and refuse to". This may seem wasteful to the extreme right, but it's a good thing. It limits government's power to abuse the less well-off. Marxists and the associated ideologies see bad people as mortal enemies that deserve either a complete conversion to the ideal class, or starvation if they are too stubburn. This intolerance can easily be directed to previously good people, once someone can convince enough people that those good people are actually bad.
Why do you think think that constitutionalism demands a centralised state? It seems a principle with fairly wide application.
Saying "constitutionalism demands a centralised state" is like saying "traffic law demands driving". The need for driving comes from elsewhere. A traffic law promotes driving only by making it safer.
That depends entirely on what you mean by "liberal institutions".
1. Protection of free speech. This inhibits propaganda and indoctrination.
2. Protection of the body, which comprises due process and innocence presumption.
3. Protection of private property, which precludes many kinds of state coercion.
The most important part is that these protections must apply as indiscriminately as possible. They protect bad people as well as good people, which is by itself a restriction on the government: it cannot identify people as good or bad without a lengthy and difficult process, even when the case is evident. Protecting bad people and evil things that happen under capitalism is the price of protecting good people from worse things.
For the first, I would've thought it was rather self-evident. That, at least, should not be a point that we disagree on.
As for the second, I imagine a gradual transition, so there will never be any single point at which "readiness" is achieved.
What I'm asking is when this self-evident problem would be solved. But apparently by "gradual transition" you mean "never"... Well I'm going to ask a little bit differently, just to clarify. Do you have a latest possible date when your anarchy would be fully achieved? Is it this century? Or is it 23rd century? Or maybe the 5992nd? Or is it really "never"?
Given the complete lack of context for those examples, I find myself honestly unable to respond. I simply have no idea what you're talking about.
This scenario applies when you have a central authority to distribute means of production. Either answer that, or, if you don't have an authority, you need to explain how you are going to stop me if I decided to just take all of a village's means of production by force, then demand the village population to work in my sweatshop.