@adams Ubuntu Touch is a bit more than just Ubuntu + Unity8. Until now Ubuntu Touch has only be build for Android phones, so the partition layout is different (https://forums.ubports.com/topic/1296/partition-layout). The root file system is read-only, there is app confinement, we access the hardware via libhybris (to be compatible with Android drivers) and so on (there are 400 UBports repos on github https://github.com/ubports).
In my opinion, as a first step it would already be nice to have raspy images with Ubuntu+Unity8 running for testing. Next step would probably be what Rodney says.