I would argue that whatever cab we choose it should be marinised as we can't guarantee that over the life of the platform that it won't have to operate from a ship, no matter who "owns" or "flies" it originally. Can Chinook be marinised (I mean inc folding rotor heads).
As for more Merlin for the FAA - OK and a significant upgrade in some capabilities, but very expensive & you won't therefore get one for one vis a vis Lynx. The Merlin would need an upgrade as it has no air to surface weapon system at the moment or Passive ID System (as far as I am aware) the and the Mk1 that is currently in service doesn't actually meet the original service requirement of being able to take off in sea State 6 and have 4 hour time on station. That may be OK in the different threat environment that now exists, though.