How to disable Virtual Server in LTM using TMSH command?

Here's an idea. Put the client name in the description block of the virtual server definition and use a shell script like this:

!/bin/bash
if [ -z "$1" ] || [ -z "$2" ]
then
    echo "Usage: clientdown.sh [CLIENTNAME] [UP/DOWN]"
elif [ "$2" != "UP" ] && [ "$2" != "DOWN" ]
then
    echo "Usage: clientdown.sh [CLIENTNAME] [UP/DOWN]"
else
    output=$(tmsh list /ltm virtual one-line |grep "description $1" | awk -F" " '{ print $3 }')

    if [ -z "${output}" ]
    then
        echo "No client found by that name"
    else
        for LINE in ${output}
        do
            if [ "$2" == "UP" ]
            then
                echo "Enabling virtual \"${LINE}\" for client $1"
                tmsh modify /ltm virtual ${LINE} enabled
            elif [ "$2" == "DOWN" ]
            then
                echo "Disabling virtual \"${LINE}\" for client $1"
                tmsh modify /ltm virtual ${LINE} disabled
            fi
        done
    fi
fi

I didn't bother making the command line arguments case-insensitive, so you'd need to have a naming/case convention for your client names (or modify the script). This will search through the VIP list for a given client name in the description field and then enable or disable those.