Theoretically it is possible to make your tablet into a screen.
You could make an app that communicates with a custom made driver that tells you system that it is a screen and then send all the data to the tablet as if its a screen over usb.
There already are usb touch screens, so it should be possible.
However, all usb screens fully get that data from the cpu, not the gpu not a gpgpu just the cpu and the R-pi probably isnt stong enough for that.
-while im looking for the specs of one of those screens i find this
So there already is software for it, but it looks like its via wifi not sure..