All along the Watchtower

At the start of the year I resolved to make a terrain piece a month. I have been diligent enough only missing one month. I have managed to make a hill, some obstacles and a shack. I want to build up some more buildings and so for this month I intend building a Watchtower. I started yesterday with the cutting and gluing. Now I have come to a little problem, the door. I don't know what to do for the door of the tower. The tower will consist of three levels. The bottom is an iron plate structure rivetted together. As has been pointed out to me before stuctures in the Iron Kingdoms need to withstand a pounding from Warjacks and Wwarbeasts so making the level they can reach out of iron makes some sense. The next level is wooden as will be the top part of the tower. I don't want to make the door out of metal dispite the logic of it. I think it would just blend in too much with the walls and be rather boring to look at. I don't just want a wooden door either as I think it will be too flimsy to be realisitc. I came up with a hybrid as shown here and I was wondering what everyone elss opinions are. I will add some hinges and a handle eventually but I don't want to start doing that until I know that this is the design I will go with.

This is a better shot of the tower as it currently stands. I haven't detailed the wooden level much yet. It will get some shuttered windows and support struts for the uppermost level. The upper level will overhang the rest of the tower by about 1cm all around. I will detail it pretty much the same way as I have done the wooden section here. I will add a good few windows and a metal roof like the last building. This will probably take a while to do as all the wooden pieces are really annoying. I am using bass wood which is better than balsa but I have to sculpt the grain onto each piece. The wood is resistant enough to make this an annoying process. Other than this I don't have much more plans for the tower. It can be based on a CD so its not a massive terrain piece that will dominate the board. The height will give it a good visual strength I hope as it should be just under a foot tall (30cm). Please let me know if you have any suggestions!