Well ascencions in general to me mean they provide a species wide buff or rework the system that you currently have in a pretty drastic way. For example synths mean you no longer need food at all. Or Transcendence gives you a repeatable bonus with brand new components for your ships available quite possibly. Or gene modding allows you to remove positive traits and gives you access to brand new traits.Well if you REALLY want to re-engineer APs then I think we'd want to throw out the entire AP system and start from scratch. Most APs are in the end just simple buffs to your empire. Heck even most species ascension can be boiled down into Leader, Worker, Specialist buffs. There's not much that really alters gameplay in any meaningful [other than role play] fashion.
Now if you really want to talk shop then I agree with you on one point -- APs should be empire defining and completely change the dynamics of the game when you take them. APs should allow you to break rules, replace old systems with new ones, etc.
All of them provide fairly significant changes to your species at least, sure they're not the most sweeping thing of all but they are significant.
So I would expect the new ascencions to be the same, for example the pacifist one I'd imagine the rank1 requires that you have robotics technology and allows robots to become soldiers but your pops can no longer be soldiers, and I'd give you flat bonuses to some stuff, but on rank2 you'd gain access to the more sweeping changes, a special project to develop non-lethal weaponry allowing you to capture pops when fighting fleets, a brand new chemical bliss sort of state that you can use on pops to change their ethos to pacifist at an increased rate, and you should gain a pacification war goal option that you can only use against empires that have been the aggressor in a war in the past X years or are currently in a war, basically anyone who displays aggression you can "attack" them but you don't kill them, you just drug them all up and they become part of your pacifist utopia, kind of like a total war but only for pacifists with set requirements.
but maybe you don't like that idea, in which case I have one for slavers and one for millitarists, I am not sure if you like those more or not. It doesn't really matter, the point is that it should have some sweeping changes on the 2nd rank not the first.