Dear Naemanson,

I sympathize with your frustration, as arthritis has started making some of the things I play too painful, and I can see more limitations very likely. I play Autoharp, and if you've trouble with arm strength, an autoharp is a very heavy instrument. (I can't pick it up with one of my hands, though I can play most of it's range)

I don't play it myself, but mountain dulcimer sounds a good option.

Another instrument I've recommended to friends with compromised hand grip is the soprano bowed psaltery. You need to be able to hold it with one hand while moving the other arm, holding the bow with a moderate grip. There usual psaltery shape is a thin isosceles triangle, with the notes set up so that the right side corresponds to the white piano keys, and the left, the black. A variation I've seen is having it turned on it's side, with the pins on either side of the thin edge, making it easier to reach & also had been set up on a tripod, so holding it was not necessary. This guy: Waynie Psaltery I've jokingly called it the fiddle for autoharp players, but you had mentioned fiddle as one thing you'd miss.
Whatever works for you, I wish you good fortune making music. (And shame on the person snarking about bodhrans not being an instrument - THAT is something that takes GREAT dexterity!)

Joanne in Cleveland