>There's one ship where going down in guns is definitely a possibility-
>the Mogami. She can be upgraded to the standard IJN 8" guns, or you
>can leave her / downgrade her with the stock 6" guns, at which point
>you have a Japanese Cleveland, and you can start paying US drivers
>back for the pelting you've been taking for the last 4 tiers.
>
>As a sidenote, I'm now imagining the Cleveland in
>KanColle, as a snot-nosed kid with a slingshot.
>"This is probably a stupid question, but . . ."

Ok...I'll have to take your word for that, as I haven't played much recently, and thus haven't made it to EITHER of those ships.
I assume you're referring to the higher rate of fire of the 6" guns...but, at the same time, the 8" guns almost halve the turret turn rate, from over 50 seconds to 30 seconds even. Now, admittedly, there are commander-skills around that, as well as others that improve the 6"-and-under guns, but...

...!
Gott's Leetle Feesh in Trousers!