I remember that Hitex has an emulator with 1MB memory
that can handle 32 banks with 32K each or 16 banks
with 64K each.

However, each time I hear about those large
applications, I think in many cases the point
was missed, to better switch to a new
architecture, and forget that 'old' 8051.
If it's all code in the banks and not just
const data tables, I personally would switch
if possible to an 32Bit or 16Bit controller.

J. Christoph