I feel a bit like stealing your idea but I just needed to have it after I first saw your pictures, brought me back to LEGO.
I cannot believe you did really buy the 2449 in dark brown, that is like 5 Euro for 1 piece :-) Had to replace it with black because I did not even find a shop supplying more than 2-3
There are only a few subtle changes as you pointed out, the entrance needed an update because there were way too many 1x1 bricks in the frame.
I felt like there is the need for a secret entrance but I did not want to replace the BURPs in the mountain area (to save bricks) so I doctored around in the prison part and it worked out well.
While building it I noticed the tower need some updates as well because they are way too fragile especially because of the 10 studs format and the 4x2 roofbricks that are not able to hold it perfectly in shape. I did not take on that yet but I probably will in the upcoming days ;-)
Thank you for your inspiration!
EDIT: I tried to find a different window solution that your pick on the dark bluish gray windows but I didnt make it, felt like this is the most difficult part to replace with a old gray solution :(