is there any way to make it stay put?
unfortunately not, since the jjos is intended to be sequenced from within the MPC - all pad triggering and incoming midi signal is interpreted as having struck that pad, thus changing the selection off.
solving this problem would compromise this ability to select parameter zones via external controller. adding an option to turn off "select pad in GPE w/ external midi controller" would be OK, as long as it doesn't apply to striking the PADS in midi mode. this way, incoming midi would trigger the pad, but wouldn't change the selected note in GPE.
that would be the best, most ideal situation but it's a fairly cumbersome FR to explain.
what i would recommend is that he sequence the drums from within the mpc and just let them sync to logic. right now, it must drive him crazy, i can see this being a hell of a pain in the ass to tweak params in GPE.
as of now, it sounds like he might as well be using a softsampler as his drum module, like guru, battery, or shortcircuit, instead of the mpc.