With the electrical stuff mostly figured out for now, I am going to switch over to making the enclosure for the power bank. Thankfully, my 3d printer is big enough to handle this task. Here is my initial design. It still needs some work, but I think it looks pretty nice.
Here is an exterior shot. The USB plugs are on the right with the LED meter on the left. Still going to have to stick a switch in there somewhere.
Here is an inside shot. The larger grey boxy thing is the charge controller, and the two other smaller ones are the dc-dc converters.