I can drop my thought on this as I was once like you. I have to agree the “idea” does sound abit ambitious but this is where you can prove everyone wrong. If you believe in your own idea then that is enough.
Your approach is abit amateurish at best. I know this because I went down the same path. I thought too big too fast and I saw myself at the finish line before I even started. I recommend you approach this in stages. I am developing a game as well butI am now taking my time having learned from my previous game dev.
Stage 1 - General idea of the overall game. (you’ve done this already)
Stage 2 - Art and Concept Art (get as many examples as you can and put them in a file word doc)(I use wordpress for this)
Stage 3 - At this stage you will use your art and story to attract talent.
Stage 4 - Crew assessment and development of mechanics and look and feel.
Stage 5 - General world/level layout. (this is important because you do not include textures or finished meshes. Layout the level/world and make sure that your character(s) flow)
Stage 6 - Resources and model archives.
Stage 7 - Full out development, Gui, animation, music/fx, lights, textures, etc…
Testing and so on…