Cost, technology and size of market are the main blocks to doing this.
First, the technology has moved so much that very few people have the chip making facilities to make exact matching chips. If they tried it with today's technology the timing and compatibility would probably stop it from working on 10 yr old machines anyway.
Cost, the cost is enormous to set up, design and start production and you need a good size run of chips to make to make it worthwhile and to be honest, the size of the market is so small, that no company would invest in that sort of money unless they can guarantee a high return (which I'm afraid is impossible).
The only way forward to to forget the classic Amiga and concentrate on the A1 and AmigaOs 4. It needs developers, it needs software and it needs users to succeed....
