Unfortunately the 1000v "vemcmd's" are not supported through vMA at this time.
You have two options:
1. You can execute vemcmd from the VSM (assuming your VEM module is online and connected to the VSM).
Ex. module vem x execute vemcmd show port
2. The other option is to log into the ESXi "unsupported" console to execute your commands.
I'll let you know if I find any other vMA or vCLI related tools that can assist.
Regards,
Robert