Wow, this is a very nicely detailed, written, and referenced concept document, covering all the bases and making me genuinely interested to see how the game turns out!
There is a heap of creativity here, and I love the weapon names, and think its awesome that you've already started thinking about level layouts including the all-important tutorial level, which will definitely be needed for this somewhat novel concept.
There's the potential that you may not end up with time for all of the key features listed, however each individual one on its own isn't particularly too much work (except for maybe the upgrade system, and depending on how its done, multiple endings), but its great to have all of these documented, and then prioritise them.
Heaps of thought has gone into this, this is impressive work well done!