As far as I am aware SRAM and PSRAM are the only types of PCMCIA memory card natively supported by the system.
Though I haven't actually tried putting workbench on anything other than a SRAM card, I have a suspicion (Correct me here if im wrong...) that since any specialised software, if required, would need to be loaded prior to workbench being able to access the card, having workbench actually on the card itself wouldn't work - Unless you could hack the ROMs and patch them manually to detect and access your card.
Btw, I had a 1MB SRAM card with my workbench system on it for a while before I got a 2GB HDD for the A1200. The system had to be totally stripped down to just about nothing, and any programs or user documents had to be stored on floppies.
Hodgkinson.