Lambda the Ultimate

Since LtU members are so knowledgable on programming languages, why don't we design the (ultimate) programming language? let's all post our suggestions here to make a lean-and-mean programming language. It would be a experiment filled with fun. I can make the compiler, if a 'standard' comes out of this. I apologise if this has been proposed before (and obviously failed, since there is nothing out).

My initial suggestions are two:

1) put as less as possible into the compiler. Make the language so versatile that all high-level concepts can be easily done with the core constructs.

2) the lowest level of the language should map directly to the hardware, i.e. must be some kind of assembly, in order to allow for very low-level programming. But the language should be versatile enough as to provide the means for doing layers upon layers of abstraction, so one chooses the appropriate level of abstraction for each particular type of application.

In the GHC Users' Guide:
Notice that GADTs generalise existential types.

And Martin Sulzmann gives us A Systematic Translation of Guarded Recursive Data Types to Existential Types