Is it permissible to delay the Maghrib prayer by 40 minutes during Ramadan to allow people to break their fast and catch the prayer, provided that it is ostensibly combined with the 'Isha prayer, and is this permissible throughout Ramadan, or is it considered contrary to the Sunnah?

The Sunnah is to pray Maghrib promptly at the beginning of its time. Delaying it beyond that is contrary to the Sunnah, and it might not even be valid according to those who believe that the time for Maghrib is short. People can break their fast with a little food, then pray, and then eat as much as they wish, thus combining the Sunnahs. Delaying the prayer is not a sin, but it is contrary to the Sunnah.