For that matter why discount the possibility of new wet build airframes to reduce the maintenance penalty accrued by maritime use?
That reminds me, the UK and Dutch Apaches have been modernised for maritime operations (anti-corrosion coatings, tie-down points, etc), and I imagine this is a capability that the Army and Royal Navy would be loathe to lose.
Are the bog-standard AH-64Es marinised in the same way?