avoid arpspoofing and seperate clients not together same unsure pool

We know it all very well:

There is this cheap standard router, where all clients no matter, how they were connected, swim like little gold fishes in one and the same 256 subnet pool. All those connecting clients are often not really seperated from all other clients, the best way for hackers & arpspoofers to do evil monkey biz

This is a new concept, where each connecting client gets a seperate subnet with only 1 free IPaddr