Although I'm not missing the last bit of my thumb I have small hands and I find the ambi controls on my HK P30 the most comfortable among many of the options presented. The paddle mag release can be hit with my index or trigger finger as opposed to my thumb and with the version I have the ambi safety can be easily manipulated with my thumb in/around the knuckle point, as can the rear-mounted de-cocker. The paddle mag release on the Walthers and some other European guns might fit the bill too, at least as far as the mag release is concerned. Slide release can be manipulated with the trigger finger as well, but it feels a tad awkward to me. That's with a DA/SA trigger, some of the options aren't available if he goes with a LEM/SAO trigger.