I think the cost is too prohibitive. At 6 mana, you will never have a complicated stack. If you were going to do it that way, what about something like:
Screwed Up World - 6
Artifact
3, T, Sacrifice this: Split Second: Choose new targets for all effects on the stack, and reorder the stack.
There's a better way to phrase it, but I think that might approach is potentially better.
I costed it at 4UU because Time Stop is costed at 4UU. I felt the two effects were similar enough in scope to cost the same.
However, you have a point. It needs a bit of work.