#!/bin/bash -e
# echo not yet
# exit 0

groupname=games
grouprealname='Unix Games'
groupid=$(dscl . list /Groups PrimaryGroupID |awk '{print $2}'|sort -rn|head -1)
groupid=$(( groupid + 1 ))

sudo dscl . create /Groups/${groupname}
sudo dscl . create /Groups/${groupname} RealName "${grouprealname}"
sudo dscl . create /Groups/${groupname} passwd "*"
sudo dscl . create /Groups/${groupname} gid ${groupid}

exit 0


To create a group, add some users and enabling remote login for the same group from scratch do the following:

Locally:

Create group:

sudo dscl . create /Groups/servsupport
Add some details like real name, password etc.:

sudo dscl . create /Groups/servsupport RealName "Service and Support"
sudo dscl . create /Groups/servsupport passwd "*"
sudo dscl . create /Groups/servsupport gid 799
Use an unused groupID number as gid! You get a sorted list of used gids by entering:

dscl . list /Groups PrimaryGroupID | tr -s ' ' | sort -n -t ' ' -k2,2
There is also an answer somewhere at apple.stackexchange.com how to find the first free uid or gid greater than x and how to apply it to new groups or users.

Add an admin user (here I assume the user name is admin):

sudo dscl . create /Groups/servsupport GroupMembership admin
If you want to add a second user use the subcommand append:

sudo dscl . append /Groups/servsupport GroupMembership admin2
Test whether the group SSH Service ACL exists:

dscl . list /Groups PrimaryGroupID  | grep com.apple.access_ssh*
If the group doesn't exist create it similar as the Service and Support group:

sudo dscl . create /Groups/com.apple.access_ssh
sudo dscl . create /Groups/com.apple.access_ssh RealName "SSH Service ACL"
sudo dscl . create /Groups/com.apple.access_ssh passwd "*"
sudo dscl . create /Groups/com.apple.access_ssh gid 399
Add the group servsupport as nested group to the SSH Service ACL group if the SSH ACL is already enabled:

sudo dseditgroup -o edit -a servsupport -t group com.apple.access_ssh
or if SSH ACL are dsiabled:

sudo dseditgroup -o edit -a servsupport -t group com.apple.access_ssh-disabled
Enable remote login:

sudo systemsetup -setremotelogin on
A script doing essentially this except creating a new Service and Support group is available here: add_localadmins_to_ssh. The linked script requires slight mods to meet your requirements.

Based on the linked script I made a new one meeting your requirements. Take it with a grain of salt and test it thoroughly:

#!/bin/bash

# set the input for lazy convenience
IFS=$' '

# We first need to test if the access_ssh group exists and create it if it doesn't

/usr/bin/dscl . list /Groups PrimaryGroupID  | grep com.apple.access_ssh* >  /dev/null 2>&1
rc=$?
if [[ $rc != 0 ]]; then
    /usr/bin/dscl . create /Groups/com.apple.access_ssh
    /usr/bin/dscl . create /Groups/com.apple.access_ssh RealName "SSH Service ACL"
    /usr/bin/dscl . create /Groups/com.apple.access_ssh passwd "*"
    /usr/bin/dscl . create /Groups/com.apple.access_ssh gid 399
fi

# create  "Service and Support" group and add admin users

localadmins=$(/usr/bin/dscl . read /Groups/admin GroupMembership | awk -F': ' '{print $2}')

for account in `echo $localadmins`; do
    # add additional blocks like >> && ! [ "$account" == "username" ] << for additional exclusions
    if ! [ "$account" == "root" ] && ! [ "$account" == "itstech" ]; then
        userID=$(/usr/bin/dscl . read /Users/$account | grep GeneratedUID | awk '{print $2}')
        if [ "$userID" != "" ]; then
            # Test if the servsupport group exists and create it if it doesn't
            /usr/bin/dscl . read /Groups/servsupport > /dev/null 2>&1
            sc=$?
            if [[ $sc != 0 ]]; then
                /usr/bin/dscl . create /Groups/servsupport
                /usr/bin/dscl . create /Groups/servsupport RealName "Service and Support"
                /usr/bin/dscl . create /Groups/servsupport passwd "*"
                /usr/bin/dscl . create /Groups/servsupport gid 799
            fi
            /usr/bin/dscl . append /Groups/servsupport GroupMembership "$userID"
        else
            echo "$account has no local GUID"
        fi
    fi
done

# Add the "Service and Support" group as nested group to the SSH Service ACL group depending on the state of SSH Service ACL.

GroupState=$(/usr/bin/dscl . list /Groups RealName | grep "SSH Service ACL" | awk '{print $1}')
dseditgroup -o edit -a servsupport -t group $GroupState

if ! [ "$GroupState" == "com.apple.access_ssh" ]; then
    /usr/bin/dscl . change /Groups/com.apple.access_ssh-disabled RecordName com.apple.access_ssh-disabled com.apple.access_ssh
fi

# Enable Remote Login service

systemsetup -setremotelogin on
In a managed environment (OpenDirectory or AD) with OD/AD users/groups with local admin access permissions it's much simpler.

If you've already created the group you can lookup the groupID and the group name (servsupport above) by right-clicking the group name in "Users & Groups".