If you can attach a PCMCIA card that already has an Amiga driver, would it not be fairly straightforward to adapt the driver to work with this configuration?
Hmmm... It depends on how you connect It. If you are able to mimic the gayle's pcmcia interface, yes, you can use standard drivers.
PCMCIA work similar to Amiga's autoconfig.
There are three memory mappings on the PCMCIA bus. The config space, the memory space (up to 16 Mb) and the I/O space (up to 64k I/O).
On power on or reset, you have to read the required resources from the config space, and assign them. This includes the base address of the pcmcia card (within the 16Mb window fot memory and/or 64Kb for I/O) and the interrupts lines.
As you see, It's not an easy task, and there's a lot of ways of doing It.
The easy way is to interface an ISA card...
Recently, I made a linux driver for an ISA based ethernet chip that can be directly connected to the amiga bus. It's very easy to program and interface. It's the DM9000 from Davicom.
It can be connected to 8, 16 or 32 bit buses.
If you want, I can make a basic design for the amiga.