10k potential customers would be pushing it - it would probably be more like in the 100s or maybe 1k if it was actually useful. Such a low volume design is bound to be very expensive.
A PC today is almost what the Amiga would be if you extrapolate what it could do back then to present day. A PC has dedicated chips for graphics, audio, storage, network etc. and most of them uses DMA so as not to consume the main CPU. You could also compare modern gaming consoles with it since they are designed specifically for running games on a TV, much like the Amiga was.
3D modeling workstations exist already - they are often PC based using a bunch of GPUs for real-time rendering (with a networked render farm somewhere else). Same goes for video editing hardware.
Making a new computer design from scratch is a hopeless task which would require billions of USD in investments. The cheapest way would probably be to use some standard x86 hardware with a custom Linux on top, not unlike modern Macs which are based on BSD with a pretty GUI on top.
The essence here is the question - 'what defines the Amiga?'