We had six, I assume the guns would still be in reasonable condition. I assume all the rest would get the 25mm gun. While not a big fan of over arming the OPV's (I think this is really a class that should be fitted for but not with), I think reactivation of the 76mm would be quite useful. With a wide range of ammunition available for this calibre, offering significant power, range suitable for a range of missions.
The only other thing which may be useful would be space for something like Phalanx CIWS. With an anti surface model, able to handle mortars, shells, RPG's, drones etc. Pirates have RPG's, surface swarms, drones could well be be the issue for ships like this (even unarmed ones). Being part of a pool, most of the time these wouldn't be fitted with them, so cost is essentially zero. It is also a defensive limited range weapon, so in line with a OPV concept. Im not sure if the Damen design has Phalanx space, I would assume not.
That would be it. I wouldn't seek ESSM/Searam, harpoon or anything else really. An armed helo is going to be a lot more useful, and for anything else it shouldn't be anything the 76mm or 25mm can't handle or deter.
I do think the Damen design with its large multi mission bay/space would be a good fit. 25-26 kt tops speed would be very desirable. It would be hard to think of a weakness or short coming. Except perhaps building 20 of them instead of 14.