"What it really needs are better engines, a meatier tail rotor and a new gearbox"
Simples, just make the tail rotor bigger and rotate it through 90 degrees....a two-type SH force HAS to be the target; Merlin exists purely to answer the question "how do we keep AW in business" not "what the best force mix for future SH capability".
I'd agree that the Merlin Mk3 cockpit is better integrated in some ways. However, it's not fully integrated. FMS driven cockpits are fine to the user but an utter pain for PTs/CAPs trying to upgrade quickly - it becomes very expensive and difficult to do so due to the "electronic spaghetti" linking it all together. The new Chinook/Puma cockpits are federated systems for good reason. Major sub-systems are effectively "firewalled" so that rapid upgrades to Comms/DAS/NavAids can be done without extensive and expensive regression testing and can therefore deliver capability quicker (in theory...)
I think the fundemental question is not being asked; this needs to be "how can we best deliver LitM from a LPH/LPD" not "how can we keep CHF in existence as it is today". The answer, IMHO, is "seeded" FAA crews into CH47, AH, Wildcat (Green) and Puma 2 units - perhaps as constituted flights, such that a TAG of suitably qualified (and motivated) aviators with a broad spectrum of platforms and capabilities can deploy in the appropriate force mix.
It'll never happen; this all boils down to SO1 and above Command positions, not capability.