I've been looking for implementations that batch (AndX) commands
together with read or write requests, and haven't been able to find
any. So, for example, I have yet to see where READ_ANDX and
WRITE_ANDX are batched along with other requests.

Does anyone have an idea of a (relatively common) client
implementation that does this? If not, is there a reason to believe
no one would actually batch read/writes along with other requests?