So many ignorant people about how elective system works. Each and every one is saying 'but you only lose your top level title, if you lose your counties it's a bug'. Bullshit. If a landless bloke gets elected how the fuck would you give him only the empire title if he doesn't have any proper land? He simply HAS to have at least a barony somewhere. So, if a landless bloke is set to win an election and he is not of your dynasty it's a proper game over since he will inherit all your clay. Byz system is at least easy to game.
Now, try to play in the HRE where the weights are so bullshit like 'good trait +10' 'he is of my culture +10' and 'he is pious +150' at 1,5k piety. You simply can't farm piety for your heir. It's friggin impossible unless you give him a kingdom and wait till he is at least 50, so you are set to lose every election ever. And if there ever happens to be some man with a weak claim on the HRE in a holy order, he will automatically get elected because of his high piety - causing instant game over.