It took courage for the writers to include a character like kimarhi,the only non-human playable,(unless you count Seymour,I guess.)and not relying on dialouge to express his emotions/intentions.
Leaves a lot to the audience that's why this thread is so popular.
Kimarhi's motivations are fairly creative(From the micro:Yuna's Protector to the macro:Sour relations to his people)
As far as his gameplay I always changed his route from game to game,but since his HP was so high,I generaly balanced him out by following either Lulu or Yuna on the grid.
(Following Yuna could actually create another storyline,at first he's Yuna's protector but slowly becomes her apprentice.)