I think the only way to get more Memory on a 8052 is Bank switching !
But you can build a intelligent logic.
I have build a handheld system with 256 Kbyte flash EEPROM for ROM-Code.
I used a standard ATMEL 89C52 with 8K ROM as BIOS and with the routines to switch the banks.
And i designed the RAM also to the flash, so i can incircuit reprogramm the external flash.
Sascha