Same reasoning would apply moreso to NGAD. And I'm suggesting in addition to, not instead of.
A second iteration wouldn't necessarily be a "super fighter", but a cheaper, relatively conservative improvement on the existing f-22 and a hedge against NGAD delays or failures.
An updated, lower maintenance stealth coating, a slightly scaled up airframe for additional fuel and range, and an updated communications suite (that's compatible with f-35's et al)... just that would be huge. As said, an fa-18ef update.
Since the tech is 30+ years old now, it's probably to our advantage to share at least some of it with our allies. Which spreads development costs and lowers $per/jet costs.
I don't know how you envision "missile trucks" working against, eg china, but humans on-board requires missile-defeating stealth, and cheap excludes the NGAD version.
And the morale argument is what? A reason to never build an awesome fighter jet again? Cool things worthy of national pride experiencing a failure will always hit morale. But a reboot of a 30 year old jet wouldn't be the prime candidate for that, anymore than people would currently think the new fa-18 is. It's an update of what will be a ~2 generation lag behind (publicly known) cutting edge.