[Senmut]

I see the design as an attempt, earlier on, to launch fighters quickly, once the enemy is sighted. Zip out there, recover them quickly, then re-launch them. Unlike what we usually saw, with the Galactica being the last warship, the Battlestar was never designed to operate alone, the rest of the battlegroup ran interference and provided cover. But, in time, the Cylons found a way to negate all that, re the open bays.
A bit like our early carriers, with flight decks made of thick wooden planking. Okay, until the Japanese deployed a hard-nosed bomb that could pierce it easily. So, along come steel armored decks. Back and forth, back and forth.