got to skip commander (whic was possible, i think)

Totally. In fact, because he's the sneakiest bitch in the world, CSF has Bush explicitly raise the possibility in the first few pages of LtH:

Every lieutenant could at least dream, even lieutenants like Bush with no imagination at all. Promotion was at least theoretically possible; from the caterpillar stage of lieutenant one might progress to the butterfly stage of captain, sometimes even without a chrysalis period as commander.