I totally agree about the custom chipset. As I have said years ago, custom chips is the only way to go if you want to be different from al the others.
Using a NVidia GPU will not create an Amiga that can do more than any WindowsBox, only special 'better than the rest' hardware will.
And yes, I still think an Amiga comeback is TECHNICALLY possible. Today is no different from the situation Jay Miner was in 20 years ago, only further up the road.
Some people say, development is to an end, nothing to be done anymore. That's not true, that's never true.
The power of Amiga should be the mix of a gameconsole and 'office' capabilities. As it was 20 years ago.