For better or worse, I am not planning to "fight at range", and I am primarily concerned about anti FAC/fighter (beam or boarding) capability since that's a gap in my fleet's capability.
My typical conops is to be 25% or more faster than the enemy fleet so I can close range reasonably quickly. I have lots of smaller ships with 45cm spinal lasers (53 damage per hit if you get in to 60km range will ruin your day) to punch big holes, and want this battleship to both soak a lot of fire (if the enemy chooses to cooperate) and/or put reasonably rapid fire smaller shots into the big holes punched by the destroyers.
I considered using railguns, since they have better DPS. I ended up choosing turreted lasers because that allows me to get high tracking speed, which isn't important for the primary purpose of poking at open wounds, but does help if I run into FACs or fighters. I do have 30cm lasers and soft xray tech, but chose to use somethign that fires faster, again in case I am facing FAC or fighters (and particularly boarders) and want to get more than one shot at them before they close the range. My BFC is 384,000km right now, so for a target goign 20km/s I only get one shot in with the 30cm lasers, and damage will depend on where in the time-tick they cross my BFC max range. With 20cm lasers I always get at least two shots in before they close, meaning one shot is guaranteed to be higher damage and much higher likelihood of hitting.
I have not optimized the engines/armor yet... I'm trying to get itup to 60kton to take advantage of shipyard size but I also want to keep it the same speed as the rest of my current fleet (~8400 km/s).
Note that I'm not discounting your advice, just trying to explain more of the context I'll be using them in and what I'm trying to accomplish, so you can better judge the design's suitability for said purpose.