Originally Posted by Echo123

Is it possible to change enemy stats such as HP, AP, initiative etc, just like in the source difficulty mod?

Yes, it is possible, the stats file Character.txt needs to be changed to do it, all character stats are defined there.

There should be several threads with the topic of character stat changing in the modding forum already. But changing enemy stats requires quite some experience because it can become quite complex, so I would not recommend it for a start.

You could download and examine the mod 'Scales' from Nexus and look what Baardvark has done.
I believe there is currently no other difficulty mod for the Extended Edition.