I'm aware of the source, but you can't go dropping shit around on a giant arrowhead without having some idea in your head of what the giant flange on the top is for.
Point conceded - would be an unsupportable way of doing things if I were actually a starship designer working from scratch. The space usage I have for it in my head now are a series of fuel silos for the reactor, and at the back, the vertical extensions for the main reactor just underneath,which, actually, is a very natural place to put main power trunking, seeing as it's right in the middle between main reactor, the main battery, and the engine block. The front end is going to have a giant armored bulkhead separating the engineering spaces from the control and sensor positions duplicated from the bridge at the very front.
Actually the spine itself does not constrict the side-mounded HTL batteries very much. Firing forward, the point at which all the side mounted turrets can cross is about 2km off the bow, which is not a very big blind spot (and this is only for the aft-most mounted turret), and probably tactically irrelevant for HTL function (what's the minimum safe detonation distance for an HTL bolt anyway?) Firing over the spine at the other side - well, a side mounted battery is likely not to be asked to fire over the shoulder.
But to ramble on a bit - the natural "ideal" arrangement of a dagger ship's guns would probably be all centerline mounted. Actually, it's so obvious that it's odd how little it's actually seen, except perhaps with this monstrosity:
http://starwars.wikia.com/wiki/Image:Pe ... r_SotG.jpg
Apart from that ship being monstrously ugly, and alternatives starting to look like space battleship yamato, in-universe reasons - what could those be?
Convenient division by battery group? Seems silly when it can all be handled remotely anyway, though it might make the systems more reliable to have battery command near the turrets its linked too. Still, not a good enough reason.
Dangers of concentration of armament? Perhaps too many capacitors grouped together are an issue once you start taking real damage beyond the shields - capacitor power for the main armament blowing off together internally from a penetrating TL shot is not likely to be nice. Perhaps more credible.
Physical stress? HTL are going to have a huge amount of recoil, and the structure surrounding them is going to have to be specifically braced to take them. Having the entire main battery together might place yield an inefficient distribution of stresses on the ship.