Have a look at the Philips P89C66x series, they have plenty of RAM as well as Flash inside the chip. If you can get by with 256 bytes - less a few - of RAM any derivative with internal flash will do.

To achieve your goal you have 2 choices:
1) external memory (RAM and/or ROM) and some loggic to "recover" P0 and P2 - or -
2) all memory internal and you have 24 port pins plus a few depending on what you do with P3.

Erik