I made some dune roleplay empires long ago. not sure how long, but I remember habitat start was still not possible without mods, so I got a mod so I could give the guild a habitat start.
in my case I chose to make different dune factions seperate empires instead of one feudal empire. in dune the different factions have quiet some autonomy, their own interest, goals and plans, etc. for example the robotics focus of IX is because they're somewhere at the fringes of the empire so they can get away with making their own rules.
and for example no one, except the bene tleilax themselves, quiet knows what goes on on the bene tleilax home planet.
and the factions fight among eachother.
also, in dune humans never encountered aliens as they spread to different planets (well, till maybe in the later books, but quiet vague/mysterious still). so that also doesn't really fit the stellaris setting that well. so I chose to roleplay from a similar starting timepoint as in dune, with humans already spread out and the empire existing, just different factions battling it out as empires. I also took a bit of liberty with the portraits, since I didn't want them all to look like humans. fremen are the klingon-looking humanoids, bene gesserit normal humans, bene tleilax (primary race) the blue humanoids, facedancers the chameleon-looking reptillian, and the guild a more fish-looking portrait.
I did not make all factions though, I focussed on the ones I find most interesting: the guild, the bene gesserit, the bene tleilax, IX, the fremen. I think I may have made an atreides and harkonnen empire too?
the bene tleilax I have multiple versions of, since that's my favorite faction in dune, so that was the empire I played myself. obviusly go for genetic ascension each time. ethics for bene tleilax is a bit complex I think, and depends if you base it only on the original trilogy, or also on the later books from the original author. I used that later info and made my bene tleilax xenophobic spiritualists (and maybe I had authoritarian as 3rd civic?), with syncretic evolution and the 2nd species called face dancers (primary species masheikh).
I was especially pleased how my fremen-empire worked out played by the AI, they wound up going psionic ascension as one of the first ai empires in the galaxy each time. I think I made them spiritualist and militarist, and very strong on the pops.
also, in later games where I only had a few of my dune factions spawn and took a bit more liberties with my own empire, I roleplayed an empire that arose out of the scattering, which explained why there were other alien species. for example I played empires consisting of facedancers (without tleilaxu masters).
