i read an article regarding the look of pegasus.... and from what i remembered, the design for the BSG was drawn up to be like the modern new age look of a battlestar, but when season 2 was being written and the episode was being drawn up, it was decided to make pegasus, although more advanced than the galactica, to have a more retro-new age look. it resembles the classic battlestars from the 70s, with a modern touch....
the ribbs on the bsg however to me i think was either having to do with the decomisioning, however why would a military start removing armor off a carrier if its still in service?