Is it even possible to migrate the project to a different technology at this late stage of development? Surely that would lead to Duke Nukem Forever problems. There's a fairly large fraction of this forum who have no idea how video games are made and work. And even among the people who do have a grasp of that, remember that this is SQUAD's first video game project. Opting for Unity was sensible, even if it leaves KSP lacking. For KSP2, they can have more freedom. Maybe even do a kickstarter. Any game dealing with hundreds of colliding parts is going to run like a rhino, certainly, but KSP does seem run on the slower side of the possible speeds. Compare Red Faction Guerilla or (even better) Wildebeest Games "Detonate".