I can imagine a set-up where one injector (perhaps no bigger than your average five-gallon bucket) feeding six chambers located hexagonally around it, like the chamber of a revolver. The actual tubes may or may not actually revolve.
But, yeah, really any arrangement could work... It's a big enough area that, as long as we don't imagine the equipment being overly bulky, we can arrange however we feel like, really.
However, Kirk's order to arm 2, 4, and 6 might suggest three injectors feeding two tubes, and calling out the even numbers could be Kirk ordering the arming of all the, say, left hand tubes...