Very attractive ships. I do find myself wondering about the wisdom of shipping 40mm and 25mm on a ship that already has a very effective medium-caliber mount in the Oto 76; I think one could make an argument that it'd be better to pick one or the other for the simple virtue of unifying spares, ammunition, training and gunlaying. Even if, yes, on paper, some roles are better suited for 40mm and others for 25mm.
Also, do you think the STIRs on the Demeter subclass are large enough to fully exploit ESSM and Standard? I'm unsure on the former and quite skeptical on the latter.
Have you given any thoughts to the potential difficulties of going from two Speys to a single LM2500-family engine, when you're trying to run two shafts? Offhand, I can't think of any ships that have an arrangement like this. Of course, given that you have electrical drive on the cruise engines, you don't really lose any get-me-home redundancy by running only a single boost turbine. It's great, if you can figure out how the gearbox works (especially as a refit, vs. a new-build hull).
I very badly want to sign off on about fifty of the final subclass to replace the USN's Perries en masse