Upgrading your flash is theoretically possible, but doesn't make any sense.
When using usb-hdd/stick you can store everything on your hdd, which is much easier and fast.
EPROM reader/writer is not (never) needed. Your Asus can handle this in different ways.
- Firmware flashing, even when customized
- with tftp (part of winxp) you can flash your fw
- you store files into your router-ram and tell your router which file
he should store into flash (a good example is your post-boot).
This is only possible with olegs firmware.