I’m back to Il-2 after a few years and only the day before yesterday discovered that BAT exists. Yesterday I’ve discovered DCG and I’m very much in love.
 

I’ve noticed, however, that it doesn’t have many BAT new planes and maps, is there an option to add them somehow? I would mainly like to play a Coastal Command campaign using some of the new aircraft and ships with missions against enemy U-Boats and shipping. Is that possible?

You can add planes and create your own campaigns. Check right here
http://www.mission4today.com/index.php?name=ForumsPro&file=viewtopic&t=7876&finish=15&start=45

 

There is also a manual
https://www.sas1946.com/main/index.php?topic=50725.0
As is a little old, there are things that you can do now but you couldn't do then