Would be interesting to hear an in-universe explanation for why the decided to go with the rectangular Fighter wings over the newer Interceptor wings though.
Ease of construction possibly. Seeing as the shape is much the same as the Classic Tie (Heh, heh. "Classic" space ship.) the old factories could be updated to churnout hardware that looks the same, but has been upgraded. I'm thinking along the lines of Vietnam-era U.S. fighters and equipment being continuously upgraded rather than phased out for 40-so years.
(Side musing: Considering that many old ships may be classic at this point in time, do you Imperial pilots would buy red Interceptors for their mid-life crises?)

