Microshift makes standard road drop bar shifters for the Nexus/Alfine 8 speed. I actually prefer road drop bar shifters for the wrist ergonomics. Palms vertical with thumb on top keeps the wrists much straighter than horizontal bars.
Tektro RL340's brake levers offer good ergonomics & are relatively in expensive. They are for road style bars as well. They'll really only work if you have other means of shifting.
SRAM is reputed to have good ergonomics as well, but I don't have first hand experience.
None of this may be that helpful for your wifes particular kind of arthritis, but I thought I'd mention it because after 10 years of being in manufacturing, ergonomics is a big factor in how I hold the bars. Fortunately my company allowed me to change jobs when "glass hands" began to set in.
My thought is you can always have a wheel with the right hub built & installed to what ever bike you find most comfortable. It's easy, just reuse the derailleur as a chain tensioner. I like road bikes, but if you find a different kind of bike you like there is plenty of other options.
The
R&E shifter dookicky can be used just about anywhere you find convienent on any bike you prefer if you find a rotary shifter you like. It's actually just a mount, so it is not just limited to a Rohloff shifter. It is more expensive than a hub-bub, but more versital as well.
Note: IGH hubs are great inventions, but they ought not to be shifted while pedaling or applying force to the pedals. Some are better than others, but it's really, really self destructive. It's just a particular operating characteristic that should be understood if you intend to make the switch from common derailleur bikes.
Tourist bars are also a good option on many bikes & can usually be easily fitted if you find a bike you otherwise like. I found I really like the one made by Velo Orange.
Here is the late 1980's Peugeto Montreal Express mountain bike I built for my son. I have a feeling this is the direction you'd like to go. Notice the 52-36 front double & derailleur. Yet is has a Nexus 7 IGH hub and the above mentioned Velo Orange bars. It should be noted you can't use coaster brakes with a chain tensioner bike. So if you are flexible about the coaster brake requirement, any older model mountain bike could work.
20181007_130637 by
Richard Mozzarella, on Flickr
20181007_130526 by
Richard Mozzarella, on Flickr