This may be on your radar already, I'm just leaving it here to be safe:
Tor Browser 7.5, due for release on 2018-01-23, will include tor 0.3.2.9, and IMO it is important to ship this tor version (in the Whonix Gateway stable Debian repository) as close to the actual TB release as possible. Otherwise, it will be trivial to fingerprint Whonix users, because tor 0.3.1.x does not support v3 onions, but 0.3.2.x does.