It did, we had also invited Eric Bloodaxe to become King of one of the Northern Kingdoms of England. Invitations to rule would certainly make for interesting gameplay. One English Prince was invited to become King of Sicily (can't remember which one) but never managed to make good his opportunity. It'd be particularly fun to undertake expeditions with the intention of putting family members on the throne somewhere.
This happened more in the early Middle Ages (c.900), but there were sometimes palace coups to put the next closest pretender on the throne, or even further down. If a king or duke is unpopular, you could appeal to the chief vassals, form a league for your election (or they could approach you), then launch a coup, and send the incumbent into exile (who could later return with an army of mercenaries... or assassins). The same could be possible for regencies, when the next in line for the throne has more prestige. In this case at least, the child would not be harmed, but his hardline supporters might be banished or killed. The same thing could happen if your infant child inherits his or her grandfather's throne; you could claim rule in the right of your child, with a loss of prestige and the child retaining a strong claim to that title or titles. (This was a problem for me in CK1, when you are trying to conceive a child and bring it to term before your 60-year-old father-in-law keels over.)
As for outright invitation by elective-law realms, this would be interesting, but I don't know if it could be implemented. During the late Carolingian Period (say about 850-922), the heirs of Charlemagne's line (Guy of Spoleto, Berenger of Friuli, Louis Bosonid, Charles the Fat, Charles the Simple, Louis the Child...) were all contending for the thrones of East and West Francia, Lotharingia, and Italy, and factions existed for each of the major contenders in each court. So the dukes of each realm really elected or deposed whom they wanted based on a short list of legitimate candidates. Otto of Saxony's election as King of East Francia was the beginning of the end of this back and forth among the Carolingians: thenceforth, the dukes would elect one of their own, and a generation later the Counts of Paris would follow suite in West Francia.