Well, I got Akitsumaru.
4-5 looks like a resource graveyard. What lineup do you guys go on it?
It's only a resource grave yard, if you have difficulty with the last kill. I'll explain to you through what I use for that map since it might be a good idea to understand how to play this map.
4-5 is one of those extra operation maps that requires you to have a very strong fleet at hand because you're going to be dealing with a strong enemy fleet in tow. And since you're main target is an enemy installation
Harbour Hime you're going to need some anti-installation gear to aid you here.
When I play this map, I use, 1 BB/ Fast BB, 2 CV, 3 CA.
During the early runs I tend to use a slightly weaker fleet, but in general I usually use Nagato, Shoukaku, Zuikaku, Myoukou, Choukai and Haguro.
Most ships are armed with the Tpe 3 Shell + Two main guns + Seaplane combo.
The CVs are armed with 2 fighters and two torpedo bombers.
The reason for this entire set up is because this should be strong enough to take out most of the boss fleets and also have all your kanmusus have a shot against the Harbor Hime (Since using torpedo bombers only will allow carriers to target installations)
Recommendation for pathing is to take the middle path, so when you reach the active branch part, head north. South only leads to a night battle and a battleship battalion which will wreck your fleet along with the Anti-Agano/Naka Abyssal demon.

Middle path will pit you against some normal fleets consisting of usually 1 Ta-class, a Tsu-class and some other mediocre ships, a fleet a subs, and another batch of ships simlar to the first mentioned group.
If you get through that you'll face the Harbor Hime.
In her initial form, Harbour Hime is very weak and can be handled easily. She usually comes with a few floating fortresses and a Ru-class Flagship of Ru-kai variant along with some small ships or transports.
You're fleet should be able to handle here easily once you get to the boss node so that map shouldn't be too problematic. However, the entire ball game changes on the 5th and final kill.
On final kill, Harbor Hime switches up her equipment using now less planes and more damaging equipment.
She'll now use 1 plane, 2 guns and an AP shell.
For this fight I switch things up by: Using my strongest battleship, and putting three torpedo bombers and 1 fighter instead of the previously mentioned set up.
For my cases now a days, I use Iowa, Shoukaku, Zuikaku, Choukai Myoukou, and Haguro.
The Harbour Hime usually comes with a few floating fortresses, a garunteed Ru-kai and either transport or some stronger late model destroyers.
The main thing you want to hope for is that the carriers wipe out the weaker ships or event possibly take out the Ru-kai. Harbour Hime is also quite strong and will likely land a devastating blow on your ships, but if all goes in your favor, you should be able to take her down. But depending on the ships you have, it could either be done in one go, or may take several attempt thus burning your resources.
This suggest I'm going to provide to you here is optional, but for my case with Iowa, I usually use her with a set up to help cripple ships and do strong night battle damage. Basiclly I use 2 main guns + AP shell +Type 3 shell.She won't do much at the day, though she's strong enough to one shot all ships outside of Ru-Kai. But at the same time, she can do strong damage to the Ru-kai and Harbour hime despite only getting 1 shot. Follow up with night battle, you can be able take out the installation or Ru-kai with ease giving you the pathway to victory.
I hope this suggestion helps. In the meantime here's some news:
Next up date is set for
October the 5th. On this day we are to expect, to finally be getting
Land Based Air Squadrons for the normal maps. In the tweet it's noted that the Land based Air-Squadrons will be usuable for the
Deepest parts of the Central Waters (World 6).
The hint is vague, but based on this information this implies that it might be possible for admirals to finally be able to beat
6-4 without having to have lots of special anti-installation gear assuming the information is correct.
For anyone that hard tried 6-4 "Recapturing Wake Island" you probably know that map is downright hard in it's current form and requires you to have several WG42s and maxed out Ka-Mi Tanks and Daihatsu + Marines along with Type 3 shells and then.... pray... .REALLY HARD.
If Land Based Planes can be used there, it'll drasticlly improve things so much making the map MUCH easier. But only time will tell if this place counts as the "Deepest parts" or not.