As far as I understand, PS/2 is only needed for power and not for data. It would therefore only be necessary to somehow interface serial to i2c. I also came across this reader: http://www.horter.de/i2c/i2c-chipkar...pkarten_1.html which seems to be genuine i2c. No idea if it supports OpenPGP/Basiccards nor if it is supported by gnupg/ccid or pcscd, though.
I thought i2c is somehow a serial interface, maybe it is the best to start with a supported serial reader if connection to i2c is feasible.