Eliminating MAC addresses is a novel idea. I have not seen it credibly suggested before. Surely some functionality would be lost? Surely you'd at least need to redesign all Ethernet controllers around it?

Anyway, IPX, and Ethernet MAC, are different protocols with unique aims. I guess IPX was routable. But it was proprietary; it was Novell's baby, and it was serving a particular purpose for their software and network architecture. There was no sin in running it parallel to IP stacks.

The sin in dual-stack IPv4 + IPv6 is that they're the same protocol. There is nothing different in their aims, their reach, their utility or their transit networks. They're all serving the same Internet purposes, and the same protocols are both on top and below them, layer-wise. Same old TCP, UDP, QUIC, etc.

So, the only reason 4 and 6 coexist is transitional support. The only reason 4 still needs support and dual-stacking is because of a lack of 6 support. When/if IPv6 is wholeheartedly embraced, then dual-stacking is obsolete.

I'd like to reiterate that dual-stacking is an administrative pain and possibly the source of some really crazy connectivity bugs. A dual-stack system is unnecessarily complex. Eliminating Ethernet and MAC addresses is a revolutionary idea that would simplify things. But today, it is realistic to eliminate IPv4 just by widening support for v6. And that's something we should be working towards.