Magikarps doesn't loose motivation he just gets the boot.
My mystic pals set up a troll tower. Their shuckle and Wobbofet stayed in for three rounds - standard - my shiny got kicked after the first one. Did not test to see if cp us a favor. However his shuckle was only 100 points or less higher than my karp.
Might be worth testing with some of my level 1 wonder prizes.