There are many opportunities to explore, but this one is better be dropped.
It is safe to say that Mary Cooper has never been a fan-favorite character. Although it was established early on in The Big Bang Theory that she was always Sheldon's favorite parent, the events of Young Sheldon showed just how unreliable of a narrator Sheldon can be. As it turns out, both Mary and George weren't exactly the greatest.
While George initially won more fans by being a fun and easy-going parent, Mary was looked down upon for her devotion to the church and her overly strict household rules. She was also accused of playing favorites with Sheldon, since she naturally spent more time and attention on him as their only child with special needs.
Now that the majority of fans have changed their perspective by seeing Mary willing to leave her whole life behind to give Sheldon a chance in life and move to Germany with him, they are wondering about Mary's fate in season 7 of the show. There are many ways for her character to evolve and move forward.
But there's also a possibility that could send her back a few years, if that's the path the writers choose to take her character.
Many fans feel it's important for Mary not to go back to the church. Of course, now that Mandy has agreed to marry Georgie, it's likely that Mary will be reinstated if she wants to. It can also be shown as an act of regaining her power and proving Pastor Jeff wrong, but it's not exactly what people want to see.
The Baptist Church has made Mary's character even more one-dimensional than she was originally created. It would be nice to hope that seeing the injustice in former Pastor Jeff's decisions would make her unwilling to go back to that part of her life herself.
It would also send an even stronger message to those who have been manipulated in similar ways before.