Got confirmation from Marketo Dev Relations Team (David Everly) that it is possible to schedule Marketo email campaigns via the following PI Calls:
Update Program Meta and specify startDate and endDate.
E.g. POST /rest/asset/v1/program/1020.json?startDate=2019-08-05T05:00:00-08:00&endDate=2019-08-12T05:00:00-08:00
2. Approve Program
This would allow us to support Automated Campaign Launch for Email program types.
To be confirmed: Does Step 1 affect the program visibility in Marketo Calendar?