I bought Drivehub on a whim to see if it would work with GT Sport and my Fanatec CSW V2, V3 Inverted pedals, and Shifter, and I'm here to report that it works pretty well. After a lot of tweaking, it feels like my old Logitech G25 on GT5 & GT6 on a PS3 (which was pretty much what I was expecting because the Drivehub simulates a G29's signals back & forth with the PS4).
Drawbacks so far are that the brake sensitivity/load cell is not configurable (I have to press really hard on the pedal...I have the Fanatec Brake Mod)...consequently I have to run ABS at default. So far I've found that if the FFB is configured too strong, it can feel notchy and loosen up on tight corners. Also, in race dial adjustments like TCS level only allows 0 or 3...not any setting in between.
I needed to change the settings on the CSW to SEN 500, DRL 005, FOR 30-50 (depending on the car)...the rest can be the defaults.
In GT Sport I set the Advanced Controller Settings to Sensitivity 1 Torque 4 FFB 10. Also, Countersteering Assist set to Strong seems to help.
It's a bit lighter than I'd like, but I've been competitive with these settings and set my best lap times.
Drivehub saved me at least $200 over buying a G29 or better just to play GT Sport....also, I did not have to dismantle my rig in order to play one title. I might even go buy a PS4 Pro with the savings.
I'm hoping Polyphony Digital updates GT Sport to support the native CSL Elite soon, and I can run in Fanatec mode vs. FanaLogic mode....and finally be able to tweak brake sensitivity.