The small Dutch navy has for years worked with the Doorman class M-frigate, which displaces 2,800 tons standard and 3,320 tons full load. It is a well rounded, very effective ship, with a big heli, 2x2 fixed 324mm tubes for ASW torps, 2x4 AShM, 16 Sea Sparrow VL or 32 VL ESSM, 1 Oto 76mm Rapido naval gun, 1 Goalkeeper 30mm gatling CIWS, 2x 20mm cannon (and it could easily house an extra 30mm Goalkeeper forward of the bridge, if needed). PNs F22P are about the same size, but less modern, esp. where SAM is concerned.
I don't see a need for a bigger ship, unless perhaps a dedicated AAW frigate with at least an SM2 VL or equivalent missile added to the armament and associated longer range radars. But one could well develop an AAW version of the M-frigate by deleting the heli/hangar and parking a big VLS farm there for longer range missiles (which is how we got the AAW L-frigates, based on the GP S-frigates, which were the (slightly larger) M-frigate precursor)
A core of 3-4 AAW ships plus 6-8 GP frigates, backed up by 6-8 smaller ships (e.g. Sigma 9113, modern-day Minerva class, Commandanti class > around 1500-2000 ton > helideck and at least rearm/refuel capability, 2x2 ASW tubes, 4x2 AShM, 16 SAM (= 4 cells Mk41 or 8 Mk48), 76mm, Goalkeeper, 2x light cannon) and 3 AORs (2 Goalkeeper, 2x Light cannon, pedestal mounted MANPADS, up to 3 helicopters) . 6-8 submarines. Some multi role inshore vessels for patrol and minewarfare (hunting, sweeping mainly). Maybe some landing ship logistic, which combined marine transport with small vessel support roles.
HNLMS Van Speijk M-Frigate
S-frigate (Greek export version. 3,600 t standard and 3,900 t full load)
L-frigate (3,000 tons standard,3,750 tons full load)