Capital ship turret capable of mounting 2 large slot addons, or 2 small-slot addons. 4 grid + 4 grid + controlling hardware ~10 grid?

I am not sure I understand your idea here fully. You mean to be able to cram for instance two neutron 2's or jackhammers in a single turret, with a grid usage of 25% of the total of the equipped weapons?

No, cumulative total grid + overhead (25% sounds reasonable)

Shouldn't get free weapon grid.

-1

I think:

A large port should be able to mount any small port weapon.

A turret should be able to mount any large or small port weapon.

Zero extra.

A turret has the ability to provide up to 25 (?) Grid of power. That means the power conduits, supporting framework, and bulkhead are sized appropriately to handle the load of a larger weapons system. Even if electrically compatible with smaller interfaces, small slot devices would generally require an adapter. Consider the various types of USB... Type A and type C. You can't just plunk a type C into an A slot without an adapter.

Nesting small into larger may make sense, but turrets aren't slots; turrets HAVE slots.

The gem turret has two.

I'm just saying to take it to,the next logical progression and create a turret that takes add-ons... Not necessarily restricted to weapons.

Inc has already stated that turrets are basically just tiny ships (without engines, I presume) glommed onto the capship.

Roda, you said -1, then agreed with half the proposal. So, which is it? -1 to two nounted weapons, but +1 to a single slot turret?

I have no problem with a small port weapon fitting every port/turret.

I do have a problem with making large port slots or turrets way too powerful.

A moth with two chaos (two large ports) and then 6 more chaos (two per turret) is way overkill.

(but I am fine with a five chaos moth)

A moth's grid would not support that load + overhead.

maybe propose addons like port adapters with a grid impact?