Why would you bother to "upgrade rear hub internals"???
I'm with
@lovinthehd on this one, that is likely not gonna be worth it for a road/gravel bike. Honestly, I think the vast majority of casual mountain bikers won't really notice the difference either--Just in technical climbs it might be worth it.
Nice bike!
Personally, I'm not a big fan of drop bars. Only have those on my road bike, and I think for a gravel bike I would prefer flat bars. I have an older 29" XC bike that I'm likely gonna convert to a burly gravel bike.