I actually think that the Crown Authority-Succession relationship is backwards.
If you have elective succession then you don't really have absolute control over your vassals. It should probably be that you need to change your succession laws first before you move up higher in crown authority.
Actually I think elective can be the most powerful type of succession, ideal for Absolute authority. You can be powerful enough that the person you choose to succeed you will succeed, and voting is simply nominal, as everybody would vote for your successor because you're so powerful. I'm not sure how this would be modeled in the game, but the early Roman Empire offers a great example.
In Primogeniture you have little control over what your first son will be like.
In Seniority it's even worse.
In Gavelkind you lose half your power and gain a rival with claims on your titles and often near-equal power to yours. The worst.
In Turkish you get lots of claimants; this is maybe the "least bad". When your ruler gets old, just give most of your titles to your preferred son (weakness: can't give to nephews, cousins, etc.).
The Roman Empire was nominally elective its first hundred years or so, though nobody in the Senate dared go against the Emperor's "vote" (decision) on who his successor would be. The Senate wasn't part of any feudal system, I know, but while the Republican Consulship was elective, many families had many members who were consuls (often 20 or 30 years apart, though). This continued after Julius Caesar became permanent Dictator, and after Augustus became "Princeps" or "primus inter pares" [Emperor].
So an important part of the government the executed the Emperor's decisions and was a legitimate vehicle for his power was elected.
The Senate also supported one general or another in the Empire's numerous civil wars, and their acceptance can be seen as a legitimizing agent to a newcomer's turbulent reign.