8 Mb CHIP RAM on All Amigas

[DamageX]

WinUAE could probably have 1GB of chipmem if the programmer(s) felt like implementing it. But if you want it in real hardware then you need to make a new Agnus/Alice chip with a wider address bus.

[DamageX]

hmmmm Im pretty sure I have read you can have 4mb with a CyberVision64 or Picasso

Nope, this is absolutely not the case. 2MB is the limit. Seriously.

PiggyBacking Chips on one another just might work

Not a bad idea, but still the answer is no. The trouble is that Agnus/Alice has many different DMA channels and stores different addresses for each one. When Agnus/Alice accesses chipmem, there is no way for any other piece of hardware to know which DMA channel is being served, so there is no way for any other piece of hardware to provide relevant additional address bits.