I've never modified the Calmini setup (my rig is SAS'd with a D44 now), but theres no reason that it wouldnt work. The bearings would completely eliminate the wear that is showing up on the arms. With the spherical bearing setup, the bearing to arm contact is static and all movement is entirely within the bearing itself.

I've looked at the dimensions of the Calmini arm, the bushings, and the mounting bracket, and the bearings I found will work well with it. The Calmini bolt is 1" diameter so should work perfectly with the above mentioned bearings. Like I said, any machine shop will know how to do it... just tell them exactly what you want and take them all the parts so they can machine it and assemble it for you.