Guns are not much used in modern destroyers, especially in escort duty as they are not really effective at engaging air targets and not capable of attacking submarines at all.

Then there are CIWS, which can provide self-defense for the ship they are on but can't really protect other ships. 1 or 2 per ship are enough but if we split a destroyer's capabilities to multiple hulls we might need more or just accept that if missiles get past outer defenses they can hit our drones.

Outer air defense, which can cover other ships on the fleet, being a very important role for modern destroyers. It's accomplished via missiles of various sizes and necessitates expensive electronics such as air search radars and fire-control radars. Those are housed in vertical enclosed tubes and are also fired from them. Current US destroyers have ~90 of those as does the plan for the future replacement.

We certainly are not going to make a ship for each cell but we presumably are going to split it some otherwise the ship will be practically the same size as the current destroyer. Of course we are going to have to replicate some elements and/or add new networking equipment to make things work. It certainly ain't going to be cheaper or more robust than the current destroyer for the same amount of missiles.

Then there are 4-8 anti-ship missiles per destroyer, we could put those on a drone along perhaps along with the torpedoes. We are going to need a surface radar for those.

Then a sonar array (and torpedoes maybe) for the anti-submarine role.

There are also some self defense measures (electronics and decoys) that the destroyer have. Maybe we put then on some of the drones that we deem more important?

But the point is why? What you get will be more expensive unless you choose to reduce capabilities significantly, less robust, less survivable and probably less seaworthy (if you are envisioning lots of small ships).

What is the benefit ? Reducing crews? It is already being done via automation to the extend that it is possible. You also still have a crew (and the ability to increase crew) if the automation is not performing well unlike the case with a drone.

Also your existing carriers, they already carry stuff, you can't just have them carry the drones around nor do they have the means to safely attach them somehow.