Comment by TuringTest

Funny that your #1 requirement, for me, would be turning coding into mostly visual reasoning. Different skillsets, I suppose.

I think of code as laying out the results of a program execution (in terms of changing GUIs or lists of transformed data), and then building up an abstraction that captures all the instances.

So, a visual tool that let me paint examples, and build (named) abstractions that group them, would be my ideal development environment. Spreadsheets are the oldest somewhat supporting this desired workflow, and things like Brett Victor's Ladder of Abstraction or tools like http://aprt.us/ are the next level, but still fall short.