It sounds like it could work out. I can't see any drawback to your designs. Rolling it would be easier then turning a tumbler I guess. I can't turn tumblers myself. The only problem would be like all tumblers it will have a drainage problem. It could get too wet. I would have made a bin by removing the bottom part and putting it on the ground. There could be some contamination from the barrow, but maybe not. It might actually work out great. Just don't add water or at least very much water.

As far as drainage, I did make sure to put the holes around the bottom and middle in the barrel. I think I will make another use for the wooden box, seal it somehow and then use it for storage of my garden tools. If I decide I want to make one later I have access to all that I want at the parts warehouse down the street. They have stacks of cedar pallets and those boxes that otherwise get shipped to the dump. They have no trouble with me taking them as I am a constant customer and a former employee.

Yes, I did notice you said drainage holes, I am not sure how well holes will work compared to no bottom at all. I am sure that no bottom will have superior drainage. If the holes are too big the compost will fall out when you roll the bin, right? So, they can not be very big, right?

I had to dry out my compost today, even just the greens create too wet conditions. I had added small amount of water, because it was too dry, so then it got too wet. It is a very difficult balance. When it get too wet, the temp goes down. The coffee grounds from Starbucks seem to contain water also, and maybe things like fruits have moisture in them. I use the compost thermometer to check all the time now.

I think it's great that you are hand turning with the garden claw. I sort out things using disposable gloves and mix them up that way. I may put all the compost out the ground out of the bin and then put it back as a way to turn it. Or I can just transfer it from one bin to another. That is why I don't need to use a tumbler, and turning too often creates a lose of heat. So, if you get into the habit of measuring the heat, you may notice a heat lose upon turning, which can be your guide as too how much you want to turn. I think every two weeks works best.

The wooden bin can be used to store finished compost until you are ready to plant something or decide where you want to use it. With a tumbler you need to take out the done compost and leave the undone compost inside. If you don't the compost is never finished. The finished compost also creates heat lose. When you mix new stuff into finished compost you get more heat lose. Heat lose slows down the process. Adding soil to the bin or not removing finished compost slows it down because only the fresh greens and browns are going to create heat.