The Huey H-1 was (and still is) far cheaper than than the UH-60. Still due to realities in production cost and production rates, the only path was a clean break. The same was true when the USAF changed from the F-4 to the F-15. Which is why the USAF demanded MCAIR destroy the F-4 tooling.
Putting two new aircraft into production? Costs a lot of money. The Army will be lucky to get one. So what is plan B? The Black Hawk is very affordable. Combine some of Sea Hawk with Black Hawk would work, although not ideal, as you point out. I had read once the Army was so delusional they believed the new FLRAA would cost no more than existing aircraft. They felt new manufacturing technology would allow this. Yeah, what are they smoking?