They could[0] implement some client side actual OTR[1], at least blocking Google from keeping the clear-text message. No idea how they would want to force the i

They could[0] implement some client side actual OTR[1], at least blocking Google from keeping the clear-text message. No idea how they would want to force the intended recipient of the message not to store it, though. [0] In theory with infinite resources and time. Maybe. [1] Or any other sort of encryption.