sorry, but the despotism has no legitimation. the leader is just the leader because he is able to keep the power... until someone else is powerful enough to take over.
Every government has to have some type of legitimation, and some type of legitimation other than force or at least maybe we can agree that force is certainly the most inefficient form of legitimation (which is why it by itself is almost never used by a government to maintain its power). If it does not who is enforcing the government? Somewhere in the structure of power there is legitimation at work, no matter when/where we are talking about.
very same principle with any other dictatorship. stalin was in power because he was strong enough to secure it after lenins death. that's the end of his legitimation. well, of course after all things were settled he was elected by the communist party of the soviet union formally as leader.
a personal cult about a leader is no way a legitimation. i don't understand how this can be mixed up. and by the way there was as much a personal cult about stalin as there was about hitler. but glorification is no way a legitimation.
Glorification is not legitimation in these forms of government yes, but it is in a straight despotic rule where you only have that to derive the leaders' power from. I don't think it is fair to say that Stalin's legitimation ended with his seizing of the party after Lenin's death, considering the sheer amounts of propoganda/the great purge/and policies put out by his administration before/during and after World War II really during his entire rule in an attempt to consolidate Stalin and the USSR's legitimacy among the people and within the party. The same can be said of Castro in Cuba, North Korea, Vietnam (which also doesn't fit the despotic designation) and Mao before his death holding on to power wasn't as simple as seizing it, and it took quite a bit of a legitimizing among the people of those countries throughout their existence. That legitimation was communism, which is why these states are commonly referred to as communist internally and externally (even though as has been pointed out several times already they aren't an exact replica of the ideal communist states envisioned by Marx).
formally a legitimation is derived form an accepted law - thats what's the words origin is anyway. if the law says the leader is elected by the people then his leadership is legitimate if he won the election. if the law says the rightful leader is defined by the right of succession then a monarch is a legitimate leader. but if you putsch yourself to power you break the existing law and have no kind of legitimation. thus you become a dictator.
though hitler won a election for the chancellor first he had to break laws to gain all the power and establish his leadership, a political coup. same case for general franco, lenin, stalin and a lot of other dictators. and correctly the soviet leaders that followed stalin are not view as dictators as they obtained their power by the soviet law and much less by coup.
the difference between (real world) communism and fascism is not the government but the economic policy. the one is left oriented the other right. dictatorship is only a description for the government and its legitimation but leaves out the economic issues. despotism describes an absolute rule but also leaves out the economy. it is mostly used to underline the use of force and often a synonym for tyranny.
all these words are not distict and not mutually exclusive. in fact you can describe nazi germany as a fascist dictatorship but not really despotic as the was not too excessive use of force against the own population (except for the jewish germans). stalins rule however deserves the attribute despotic as he mistreated his own populations severely. it was communist and a dictatorship too.
Yes the Jewish Germans, the mentally ill, various other ethnicities within Germany such as the Romani, the communists, any and all other shapes and forms of dissidents such as Sophie Scholl's white rose group and others, etc. Despotism isn't about being cruel to your own population (otherwise as you can see Hitler too clearly was a "despot" unless your definition of "your own people" is exclusionary of all the types of Germans persecuted by the Nazis) it is about having power consolidated and basing itself upon one person. Even if you want to say that is all that the USSR was during Joseph Stalin's dictatorship then (which I still don't agree with as even he had to mainly attempt to appeal to people on idealistic grounds rather than his own celebrity) how is the later USSR modeled in game? It isn't, and the politburo has no representation at all without the communism government civic. As even you said Stalin's rule was legitimated by law eventually, so I don't see how that isn't the same type of legitimation as hereditary rule where a despot decrees that power should be passed down his family line.
Monarchy is already separated from despotism because by doing this it changed the political dynamic of the nation, but I'd say the same thing happened when fascist dictatorships and Communist dictatorships were invented. Their rule was no longer just legitimated by their own decree, but they claimed (whether you believe them or not) they were acting according to their respective ideology which a truly despotic ruler would not have to do, they rule and act the way they do because they are the ruler period. Especially in the case of the USSR I think you can see this as Stalin wasn't simply replaced by another despot ruling for life, so you can see the difference at work. Whether they were "faking it" due to their megalomania doesn't really matter because frankly it worked/works even today to secure power or in other words provide legitimation for these governments. Many people around the world will claim that other forms of government in place in their countries don't live up to their supposed legitimation either (including democracy and the efficacy of the public vote), however these government's power still rely on it.
So basically the way I see it as represented IN GAME is that junta represents any kind of dictatorship (which might not be entirely perfect), but certainly not the fascism civic. Fascism can't represent dictatorship while you also have despotism if for no other reason than because that acknowledges the difference between fascist dictators and despotic rulers in which case why not distinguish communist dictators as well? Society legitimizes government, not simply through laws which can be written to say anything and legitimate anything, but there is legitimization behind the laws themselves that appeals to more differing depending on which nation/government we are talking.
I think I also need to say again that this is different from straight ideology as ideology does not have to be the form of legitimation a government appeals to for example democracy which can say whatever ideology is present, and whether you personally agree with its reasoning has its legitimacy in the vote. However it is the only one that can do this, the legitimacy of a Monarchy or Despot or Communist/Fascist dictatorship has to come from something else, no one governs without some measure of support from the people, and if you can't point to an action by the people which legitimizes it you legitimize it in other ways by god/or in the modern era by reasoning with the populace that power must be distributed this way for some greater purpose as the fascists and communists did.
