You can talk all the world about Amithlon or fast 68K CPUs. It does not fix the main issue of AmigaOS.

The memory limitation is 2GB, there is no real memory protection and only one core can be used properly. Even a 64GB X64 board will not remove these limitations.

It needs a new and incompatible OS to fix the real problems. You can speed up the processor as much as you want, but those issues will always be there.