Check http://www.olympic4x4products.com/Sport-Racks.html for some ideas.

One issue to consider is coming down the side to the frame may require some stability support.

The ladder can be done and incorporate the tail lights. There are a couple of companies that have done that for jeeps. Asfir does make a few products that may give some ideas.

The one point I have concern with is getting any weight up high without having a stability point that leaves the shortest down run.

I have a Jeep JK that I am looking at rooftop tents. There are a number of products available. A couple I have seen are sturdy, maybe even over built.