An idea! Add a button in the revolt menu, "Reform", which is a reverse rebel flag of separatists. It will mean that you, as a leader, organize a full reform of government, complete with changing politics, religion, etc. But, it requires decent diplo-tech. Let us say... 16.
Some will not like it, depending on your legitimacy/republican tradition/tolerance of true faith (for theocracies), your revolt risk and accepted cultures. If you have ideal stats, and don't leave your religion/government/culture, you will just take a minor penalty for doing so. Also, you will place it on cooldown until the next ruler's death comes by doing so.
But, changing your religion/government/culture causes revolts of zealots/reactionists/nationalists depending on your former difference of tolerances of religion/(legitimacy/repub. tradition/tolerance of true faith)/level of your new culture's dominance over your old ones.
Before you say anything, you suffer only -1 stability penalty from attempting to change these parameters in their groups (i.e. christian religion group, finno-ugric culture, monarchied, republics), and -2 stability penalty if out of their groups.
This will require monarch power, again, depending on switch. Always administrative. It requires 50 ADM for cosmetic changes, 50 ADM more for each non-cosmetic change, double for leaving groups.