And as I said earlier, you can repair those ships later at weekend when you're done with all weeklies.
For world 3 kills, the ships get barely damaged and can be healed during work time or so (assuming you have a job or similar, where you can't play the game all the time). For world 4 kills...that quest chain is even barely worth it and even then, nothing you can't repair overnight with 1 Akashi.
Saving 5 buckets only matters when you would actually spend buckets for repairing shouha ships. If you don't rush and just to the quests at the intended pace, you'll save both buckets and resources.
Concluding the whole discussion: Having a 2nd Akashi is fine and somewhat useful during events and in special situations where you have to rush things (like very busy work schedule or similar). In non-event, non-busy situations though (i.e. not ranking), there's barely any need for a 2nd Akashi, unless you're paranoid about sortieing a slightly damaged ship or simply OCD from having damaged ships in the fleet.