I would like to have the ability to restrict specific users or specific groups of users once they are connected to Meraki Client VPN. I realize I can apply firewall rules but these firewall rules apply to the entire Client VPN subnet. Since I cannot use an external DHCP server for Client VPN, I don't have a way of doing DHCP reservations for specific clients and therefore I can't filter based on specific source IP's.
Obviously Meraki doesn't have anything like ASA Group Policies. Are there an other mechanisms I can try to do this?
You could try using the Meraki Group Policies. You can set specific firewall and traffic shaping rules and apply them to specific clients on the client VPN.