Feel your pain, i have sudden onset arthritis and my most recent diagnosis is severe Rheumatoid with secondary Osteo, i have to use a wheelchair if and it's a big if, i can get out of the house and im currently medically housebound whilst i wait for multiple joint replacement surgeries (anywhere from four to eight operations on the horizon) and I need the help of at least two people to get me out of the door for Hospital appointments.
I have found that certain aspects of "bushcraft" have kept me going, whittling, carving, making cordage and general tinkering have kept me sane and importantly have helped with exercising my joints, even my physios and OT's were impressed by the level of grip i have retained and increased in my funny shaped hands and they put it down to keeping as active as i can and exercising, but they have warned me on more than one occasion not to overdo things, as im prone to doing, but i have to push myself and if it starts to hurt - stop (like i take my own advice lol)
I try to make something every day if i can, even if it's just a pile of shavings, but there are days when, as i'm sure you know all too well, it's just too painful to do anything, thankfully those days are few and far between, but even im now wondering how many more spoons, try sticks, netting needles and pot hangers etc i need and i've enough cordage to weave a blanket i think (although it would be seriously rough in texture).
To answer your question though, i've not made too many adaptations to the gear i am currently using, but I have adapted the way i use said equipment to suit my needs and requirements on the day.
On the flip side i've also resigned myself (for the moment) to accepting some of it might never get used again, but i'm reserving judgement on that until my surgeries are complete and i have some mobility back before i make a definitive decision and start offloading equipment.
I do find however that a larger handle on a tool helps some days, whilst other days a narrow handle helps, one thing i did make was what i call my "bitsa knife", its a Hultafors HVK blade set into the handle of a Mora 164 spoon knife, the larger diameter handle really does help on those days when my brain says do something, but my hands are saying "nope" and even the act of just creating a pile of shavings is often enough to retain a bit of dexterity and sanity, also not having a single set handle shape or size helps to keep those joints moving, it's all gentle exercise which is the most important thing, it would be very easy to give in to this disease as i'm sure you are well aware of, but as i say to people
"I have arthritis, arthritis doesn't have me".
By far the most important lesson i learned though and it was a hard lesson, learnt the hard way, was my life has changed massively and this disease is with me forever and i have had to accept that some things i may never be able to do again, i know i can't do the hand drill any longer as my hands are far too deformed now, but i'm hoping after surgery that i will be able to find a way to do the bow drill again, a ferro rod though, even now is thankfully still viable, likewise some things just take longer now and it took me many hard knocks to let go of the frustration and accept that it is what it is, even though some days i just want to curl up in a ball and be left alone.
Bitsa knife