There’s already a SFOS port for this device. Unfortunately it can’t be upgraded from 3.4 to any higher version.
Given that this port shares similarities to the Xperia X which is still supported this should be durable.
I still find the Xperia Z3 Compact tablet fast, thin and modern hence hoping for a more recent port.
Thread on TMO where people have tried upgrading the device beyond 3.4 and lists the errors: SailfishOS on Sony Z3 Compact Tablet - Page 19 - maemo.org - Talk