Scandals, stress, illness and vices to shake up the leader positions.

[Starfry]

Right now, the leaders are somewhat robotic. They do their jobs for over 200 turns and if they get a little pouty, they get a bonus which with a good interior director, can keep the machine rolling. This means a Cap 4 SHQ can turn a small nation into a powerhouse due to their high skills. Vices, stress, illness and scandals would shake things up where you need to make a decision to either ignore, threaten, send them for treatment or outright fire them depending on the severity of the situation.
It would make it interesting that on hazardous worlds where stress, respiratory illness and bodily disorders starts to affect their jobs and start cutting into willpower and lower the retirement age unless they have sabbaticals to recover some health.

Scandals would be another twist. Ideally, you want to keep your leaders vices in check where you make decisions to either ignore a slight drinking problem or deal with it. While dealing with the problem may give a relation drop, you have to risk giving them bonuses as it had a high chance of an inverse reaction where they take the money and worsen their vices. Scandals erupts when the public starts to hear that military directors are developing high energy weapons while blitzed out of their minds. The public would demand their resignation and depending on the government, either fire, send them into exile or ignore the public.