Aquilea is supposed to have 5 different paths, republicans, weird socialists (idk if harmony or communist), regular communists, royalists and "fascists", who are simply the party of the Leonard Rodier
In the lore he is a very good field marshal who stood by the king during the first revolution, and when the second revolution happens he oftens flees to the griffonian empire, and you can have him as a field marshall
if you play as the griffonian empire and later conquer aquilea, and have him as a field marshal, an event will pop up where he will ask you to rule aquilea as a puppet

but the wiki https://equestria-at-war.fandom.com/wiki/Kingdom_of_Aquileia
says that :
"The former leads you down to choices where you decide which of your vassals you need to prioritize, two of the four vassals you currently hold are often rebelling once you choose their counterparts over them, it's recommended to be prepared to fight whoever revolts.

Going down even further allows the player to choose either the King (Non-Aligned) or the Maréchal (Fascist) as head of state, the former is simpler and easier, though the latter, being longer, offers more bonuses in the form of national spirits, though both still allow the player to expand Aquileia and invade neighbouring nations to the east and north."

which anoyingly in my testing doesnt seem to be the case

I really want to play as the marechal (mainly because the queen has a huge beak and she looks weird, it feels like she has a terrible birth defect or something, like the griffon equivalent of ichthyosis harlequin or even elephantism, she is terrifyingly ugly, I mean who drew this, its the stuff of nightmares, she looks like some sort of furry abomination of a bird instead of a regular mlp griffon, I cant even look at my political tab without wanting to throw up, meanwhile the marechal has sun rays permanantly shiny behind him, I mean come on people, thats not even a choice)

So how do you do it? Going fascist Aquilea?