I think I just have a fundamental problem with replacing an outdated ship with another ship of identical design. That doesn't happen much in the real world.
I mean, when a military truck grows old, it may well get replaced by another of the same, thirty-year-old design, only this one is fresh off the still-open production lines. But ships are much more expensive and not really produced on "lines": the tooling is built for a specific batch and then scrapped, there is no spares or surplus production as such... And there are no advantages to be gained from standardization anyway. The last ship in a batch is likely to feature all sorts of improvements over the first - but if more ships are needed, there's no incentive for going back to the original design if this can be avoided.