i was also thinking about this idea for a while, with similar reasoning - enough possible rp is incurred, many tensions are possible, while it fits for every non-democratic regime.
there could also be some kind of forced type of elections, like lords representative type of election as the only way in appointing rulers in monarchies and tyrannies could have something like noble with highest prestige to receive short-duration opportunity to announce himself a ruler.
generally, a bit simplified, but i think it works as a principle: less customization for government, more rp, flavour, opportunities for internal tensions, more sense in governments type differentiation.