NuVinci continuous shifter I'm building a bike for a woman who injured her hands in a fall and who now experiences pain when using trigger shifters. She does a little better with grip-shifters though even their resistance gives her trouble if she has to shift often. Does a NuVinci hub with its continuous/stepless grip-shifter have a mechanism that is easier to twist than a normal grip-shifter?
BTW, is NuVinci still in the human-powered bicycle business? Some links on their web page go to non-existent pages, and they don't have any dealers in my metro area, which has over 6 million people.
The NuVinci system is quite interesting. There is no spring to pull against in the shifting mechanism, the shifter relies on two gear cables. You could reduce the required effort by using the best quality cables and housings available. There is resistance on the shifter though, not dissimilar to a normal grip shifter but without the clicks to power over. Whether it would suit your application very much depends on whether it's easier by a big enough margin to be noticeable.
NuVinci changed their marketing name to enviolo fairly recently. The products are basically the same though. https://www.enviolo.com/en/
Like you might expect, you'll only know for sure once you've tried it. Does anyone in your area use one of these systems?