The guns were 4.7" in calibre - not that there's much difference from 5" (and certainly not in 1/700 scale!).
In those days, the word "squadron" was only used for larger ships (and aircraft); destroyers (and submarines) were grouped into flotillas.
There was also additional accomodation in the enlarged after deckhouse.
You are right that British between-wars destroyers were built in batches, eight at a time. However, each batch came with one Destroyer Leader, intended to host the Captain(D) who commanded the squadron. So they had more personnel space, and the A-I class leaders also had an extra 5" gun amidships (between the stacks). And Faulkner was the class leader for the F class. So that is why everybody is saying you would need to lengthen the Tamiya E class destroyer. If you look at info online, I think you will find that the fo'c'sle was extended back to house those staff offices.
The Leaders weren't one-offs, though. I believe they were mostly in pairs, all named for famous British naval officers with names beginning with the class letter. Faulkner and Exmouth (343' loa) were twins, as were Grenville and Hardy (330' -ish loa,). The regular E class was 329' length overall.
I am not going to get sucked into any more research that would cause me to start a new project, unless you have any other questions. :-)
AJ Models or Niko makes a Hardy in resin, which is really, really close to Faulkner and Exmouth, but it sounds like you want to work with plastic, so the Tamiya kit is dandy.
for the record, most of this stuff came off the top of my head from the days when the Airfix 1/600 H class was the only game in town and Airfix Magazine ran an article on how to convert that to the destroyer leaders. Great fun.
And since you are asking specifically about Faulknor, I hope that means that you are reading or have just read "Destroyer Leader", by Peter C Smith - a wonderful book.
Admittedly, British destoyers are a weak spot in my naval knowledge.
That being said ?
Can a 1:700 HMS FAULKNOR be fashioned from an existing kit, possibly a Tamiya E class ?
Now I have heard that British destroyer classes are usually very similar next to their assigned lettered groups- as in, potentially, that E,F & G classes can be sometimes indistinguishable from one another.... is this true, for the most part ?
And what would be a good starting point for FAULKNOR; the E class from Tamiya ?
As always, thanks for any imput here & enjoy your weekend !!