This should have happened when we removed most of MAINTAIN_BACKWARDS_COMPATIBILITY artifacts. Its not practical move SHA1 into Weak:: namespace or "typedef SHA256 SHA" because SHA1 is too intertwined at the moment.
In the interim, maybe we can place SHA1 in both CryptoPP:: and Weak:: namespaces. This will allow us to transition into Weak::SHA1 over time, and signal to users SHA1 should be avoided.