Assuming there are no bugs in the ever more complicated HW. I don't see much feature creep dragging his project.
Especially when your goal posts keep moving constantly.
Lack of resources. For instance USB support adds insane amount of extra work. Why? Just because you don't want to use PS/2 like the other projects?
How much effort is adding a PCI USB controller to a board when you've already designed the PCI bus interface? The same goes for ethernet. It's hardly "insane" in my opinion.
And Natami without USB would be a strange beast given that it's meant to be a more up to date classic Amiga, and USB stacks exist for the Amiga already, and most peripherals are USB connected?
I think that the Natami people have realised about feature creep, although they did get carried away in the past with things like that 3D core. They cut back the 68070 initial plans to the 68050 too, which shows the ability to cut back to more attainable targets.
And bugs? It's an FPGA, they can get these sorted out down the line when they turn up. As long as the first release can run Aros 68k, AmigaOS 3.x, DPaint and many (if not all) AGA games and OCS/ECS games that great.