Considering that this guy published STOLEN documents belonging to the United States Government (confidential, secret, top secret), I support the move to have him brought here to the US to stand trial under espionage charges. He published over 250,000 diplomatic cabals between the State Department and our embassies, now there's the whole Vault 7 thing which consists of communications, documents, and source code that was stolen from the CIA's internal, air-gapped network. This guy needs 'el Chappo' Guzman as a cell mate.
Personally, I welcome his current accommodations. A self imposed prison sentence at the hands of a foreign nation. If more criminals could be like him we wouldn't need jails.
One other thing. The UK says they will arrest him if he leaves the embassy. The question becomes what if Ecuador grants him diplomatic immunity? Or if they sneak him out? Surely the UK is not searching diplomatic vehicles. They could smuggle him out to an undisclosed airport and send him to Ecuador.