Sorry, I cannot vote in this - since the option of time to abandon sandbox and return to normal is not on the list. My own opinion is the sandbox is a complete and utter failure.
Thailand is in dire economic life-support condition now. It needs tourists to survive - Time to pivot away from tourism is not an option in the short term anyhow.
Drip feeding tourists into Thailand is a complete waste of time, It needs mass tourism and it needs mass tourism now, not drip, drip, drip. Too few tourists arriving is as bad as none at all - a handful of people visiting a hotel or restaurant wont keep it afloat !
so option 5. Abandon Sandbox and Cancel COE, PCR tests, Quarantine, flash your vaccine passport and get on with tourism with Sandbox