That green frame is very pretty!
If you fancy a drop bar fat, have a look at @substandard8 on Insta. Rides a drop bar Ti fat smokestone. Think he has got the weight of it down to 10kgs. Proper quick as well. Finished 4th Gbduro this year.
A fat 4" tyre will be pretty squirmy on 42mm internal rims. Bit too narrow imo.
I would still go Hope over WI hubs. Not as pretty, but available adaptors mean much more versatile across different Fat standards.