I extended and modified the AppleVIAATA.kext to work with my VIA
VT6421-based CardBus eSATA controller.
It also does support hot-plugging - although not perfectly yet.
The driver is currently for VT6421 devices only but could be extended
to support the other pre-AHCI SATA controllers from VIA as well.
Do you have any interest in that driver?
As I don't have any Intel Mac the driver is tested on PowerPC only.
The Intel specific code is completely untested but it might work.
Cheers,
Tobias