You missed his point. He was saying that having different weapons combinations in a single turret should not be made impossible. Like mixing missiles and lasers into the same turret, for example.
Different weapon combos on a single turret is not impossible, just as having a machine gun and cannon on a tank turret is not impossible. However, unless the tank machine gun is on a separate turret attached to the main one, it can only turn as fast as big gun can. If you tied a pistol to an artillery gun for close range small target defense, it would still be limited by the size and turning speed of the big gun.
May I remind you that reduced turn rate means turrets would be more likely to hit slower moving targets rather then faster moving ones, which would mean that will only work if fighters were faster then capital ships which currently they are not, meaning that if the turn rate was to be reduced then there would be no point building turrets at all because they would not be able to hit anything.
This will be less of a problem when the changes to thrust are added, as fighters that can turn fast will not need to put many points in side/up/down thrust while a bigger ship will need to if it wants to be able to go that direction without turning for ages.
BIG turrets would not be able to hit small ships, only bigger ships, if turn speeds were changed. Smaller point defense turrets would still be able to hit fighters and shuttles. This wouldn't make every single turret have the same turn speed, and that speed be super slow, but rather mass based (or preferably based on the mass of the weapons systems).
You know little to pretty sure non of me or my builds to actually make a claim like that. If you would, you would know that most of my builds (if they can support it) have multiple types of turrets on them, most of them for a multi use and a mix of small and medium to large turrets.
Your claim that the idea has only benifits is just wrong, it will kill a part of the creative turret design as a turret HAS to be as small in mass as possible in order to be effective.
Do I support the use of multiple size and types on a ship, yes. Do I support your idea to kill smart designs, no.
A turret would not need to be small in order to be as effective as possible. A turret would simply need to be small to deal with fast moving ships. A small turret would not be effective against a capital ship, and a large turret would not be effective against a little fighter.
This would advance creativity because more people would build varied turrets because they actually have to, as opposed to now, where the only reason people build smaller turrets is because they lack the needed space on the ship it's attached to, or because their turret is so big that they need smaller ones to get the ships that can fit inside the turret's massive turning radius.