The goal is to have a kick-ass speed.
For me both of the points sound like a denial and I'm extremely happy that there is a PyPy team who cares about performance and concurrency. The core python team is working on minor tweaks and small-ish features in 3.x which can't hold a candle to solid 2-3x performance increase, built-in support for stackless/greenlets, extremely fast built-in subset of numpy and prospects of running your code truly concurrently with stm.
The argument was always "easier to maintain", but that said, unladen swallow was agreed to be merged into cpython, had it met it's goals.
If you want to remove the GIL and come up with a way to make the thousands of 3rd-party modules still work, please do it. Beazley has investigated it, but if you think you can do better, please do it.
The modules can be re-written. By removing the GIL, we are giving a definite power boost to the language(applies to ruby too)
Personally, if I had to go without 3rd party modules like numpy and pandas for any length of time, I might just switch to another language.
Guido should just take it like a man and accept a pull request to merge PyPy's JIT interpreter into CPython.