I like how you are trying to stay away from both movie versions of the Nautilus, too many people think that is what it's supposed to look like, but it's not. It's supposed to look more like a cigar in shape. Yours is the closest to the real Nautilus on this whole website.
I know how tough it can be trying to build something with limited bricks, but here's a little well-known secret that can give you more bricks than you thought you had:
3 flat bricks like this(::::)when snapped together form a regular brick.