I have been using an UDS for almost 10 years, so he is my .02$
If you properly build an UDS, one basket can last very long time. My basket uses a charcoal grate from a weber grill and has expanded metal for the side. I have had it smoking almost nonstop for about 40 hours on a basket of charcoal. As for the smoke wood, I put in about 6 good size chunks and a few buried in the charcoal and when I'm finished after a 20 hour smoke, I still have some wood left.
If you just want to be able to get more wood or charcoal into the UDS without having to remove the grates, which I know can be a pain in the butt, I would make a side door that would give you access to the charcoal basket
If you would like information about building your own heatermeter or having someone build one for you, feel free to ask any questions you may have.
I think the time taken to design and build/undo/redo/redesign the workings of a gravity feed on a UDS would probably be better spent just building a gravity feed smoker and have done with it. But if you are determined to go down that road, I'd definitely be looking at that interesting build.
Learning generally boils down to "Repetition or the avoidance of pain", some people learn by doing, some by watching and some just have to pee on the electric fence.
Whether you think that you can, or that you can't, you are usually right. Henry Ford