You will still need a "real" computer besides the iPad Pro, the SP4 can be your only device. This isn't even because of "Pro" apps which don't exist on iOS. Downloading of large files isn't possible on iOS. The driverless Airprint quality (looks like 150 dpi) is a joke and for some jobs simply not good enough. Batchjobs on Exif info and metadata-inspection of other files you get or want to send isn't possible. There are countless other little things which aren't possible on an iPad - "Pro" or not. These might not be everday tasks, but when they are necessary you are stuck with an iPad.