So I could get this freehub and all would be dandy?
Doesn’t sound like it, on Hope hubs:
You can’t just put a hope 11sp freehub body on an existing pro3/pro2 hub body.You need a new hub
Not sure why though, all other hubs I’m aware of are plug and play so to speak.
I’d then use a road 11 speed mech with an 11 speed cassette?
I know they don’t do a clutch mech but I know someone who ran a 9 speed xt rear mech and had no drops with 1 x10 (narrow wide on the front)
Yes, once you have an 11 speed freehub body you can use an 11 speed road mech and cassette, with 11 speed STIs. You can go single ring if you want, but you can’t yet get a LH non-STI hydraulic drop bar lever to match the R785 in your OP.
9 speed MTB and 10 speed road are cross compatible, so yes, that combination would’ve been fine.
Edit:
I bought mine years ago. It’s a mtb hub
There are two types of Pro 3 – those in the built MTB wheelset, and the non disc hubs (previously called Mono). The 11 speed ones are the latter, although I was under impression that you could retrofit an 11 speed freehub body to any of their older hubs.