NEW: Cuba's government proposed its biggest economic overhaul since the 1959 revolution, seeking to revive the economy under mounting U.S. sanctions. The plan would allow private real estate development, permit private banks, convert some state firms into share-based commercial companies, and reduce restrictions on private businesses. Prime Minister Manuel Marrero said the reforms would use market mechanisms to improve efficiency while remaining consistent with Cuba's socialist system. The 175 proposed measures require approval by the National Assembly.