I am confused essentially you keep saying the rider needs help on hills and then you suggest moving to hubs and motors that would be worse up hills? You might tell your friend to join up on the forums so we can help them better. However to help you, stick with more gears especially on the low end, mid drives (which they already have and a good one) and lower gearing but not too low gradual increments otherwise you might leave the person spinning out too often.

A SA 3 speed is a fine hub especially actual Sturmey-Archer hubs made by them (not the sun race stuff) but is not a hub I would want for climbing hills on a heavy e-bike I would want it more on a around town hybrid in a pretty flat area maybe with minor hills or just a fun vintage roadster type deal.