I have a welder and was more than likely going to do that but I really wanted to see opinions about that kind of stuff. We haven't "quite" narrowed down what TT we want but I know that some of them have the slide out storage racks on them. They seem to be fairly sturdy?
If I were to do it myself I would weld up a frame with 2-2" receivers about the width of the I-beam frame apart that way it is very stable and has no side to side rock in it and then build a full-width rack accordingly.
I think with a custom setup I can add some locking bars to it so I don't have to worry too much about theft.....