Yeah, the Startled Witch uber already has something like that with its The Sleep ubercharm, but that's not all that customizable since you can only choose one option out of 16 (which is still a lot), and more importantly, it's something that is at a high difficulty level that you can only get with a char that has already completed a lot of content because you need to do an 'Extremely Hard' difficulty uber as well as get a trophy from another.
I'm talking about something more like Sunstone of the Elements which basically every character has, except instead of getting it at level ~50 you get it at level 120 and then you cube some relatively easy to get ubercharms with it. Maybe you need particular swirlies on you to be able to cube it every time, if we need to make it more difficult, like any one of the Judgement Day swirlies.