FWIW: generics and boxed types allow you to write code without overflow, but there's plenty of real-world C++ that's full of overflows. Good C uses a small number of types and also avoids overflow...
Although we have different concerns, it's clear that a lot of thought has been put into the proposal, and it seems to achieve its/your goals pretty well. Don't let my concerns put you off.
The proposal doesn't really care much about distributions. It's intended for people who don't care about random distributions.