It doesn't make sense that it can take more turns to train an elite paladin unit than to research some techs. Yet, that will happen from time to time depending on conditons. Even if we assume that people more or less kept their knowlledge base but was unable to use until the sovereigns started resurrecting the lands (bringing back the conditions for scientific research, turns being just the time to reimplement "lost" knowledge one step at a time), there is always be a problem between the correlation of turns/research/training/population growth/construction of buildings/Scions... Should I complain that a unitonce trained is inmortal? If it doesn't die in battle, it won't die of old age or anything. So why complain if the growing of the Scion can take some more turns than a normal unit? Unless turns represent literally days and everything works based on that (the most basic building will take a few days, others will take weeks, others months, totally basic units a day or two, elite units some months if not years,...), we are going to find problems correlating turns with actions in the game. We need abstraction and we don't need to like it.
We shouldn't take Sovereign = King/Emperor and the Dinasty system as the princes and princesses waiting for the lord to die and inherit. Because it's not like that and we shouldn't think about them in that way.
The Sovereign is the King. Scions are just nobles who rule a land given to them by the King. Conditions? Scions can rule that piece of land but they serve the King, pay him taxes and their manpower is available to him in times of war (just in case the "servethe King" part isn't clear enough). The noble can keep his lands as long as the King allows him, as the only real owner of those lands is the King.
If a Sovereign dies, nobles could claim lands as theirs but as it's in the game (Sovereigns being mumbo jumbo masters), they have to swear alliegance to another King. In this game Kings might not be considered chosen by God like in feudal times but they might still be considered chosen (because anyone can bring land to life, right?) and people might not like to defy that "fact" (irrational fears, religious beliefs... choose your poison).
It has been said about neutral Kingdoms or vassal estates, so nations without a Sovereign seem possible... as long as Sovereigns allow it (or they were formed before they met any Sovereign).