I still don't get what's the point of changing the materials in the first place?
The guy brags about breaking the rules and being innovative... But why? The point of this whole thing is to be tough enough to withstand pressure. The materials all other proper submersibles use up to this point work. So why change it? Is it cheaper? Did he think it's even stronger his way? He never explained this.
I also don't understand the design. I saw a few construction videos and pictures of a some submersibles and one thing they seem to share is a spherical main chamber (regardless how the outer shape looks). It's a sphere because this way pressure is applied evenly around it. They even try to make it as perfectly spherical as possible, according to the video i saw, for perfectly evenly applied pressure:
But the Oceangate sub clearly used a cylinder shaped main chamber? Dunno, maybe that's not an issue, i'm not an engineer expert, but if i was going to put myself into this situation, a sphere would make me feel better. It just feels right.