Wouldnt you want to use a much faster hard drive to run bitcoin on such as a "Samsung 960 Pro NVMe M.2 SSD" or something of that speed? Or would that not be able to connect to the Rasberry Pi? You would think you would want something faster than 100mb/s though, especially for a public node... those usb thumb drives arent very fast...
Such an SSD would be a huge waste of resources. The latest Raspberry Pi has USB 3.0 which allows for speeds up to ~600 MB/s while that drive can perform much better. I don't think if there is any point in buying an expensive SSD for such a budget setup. A cheap HDD is enough.