Limiting clients to 1 IP address from DHCP

RouterOS General
2

Not sure of how you distinguish between your customers and how you manage them, but what you are talking about seems to me like a MAC binding use case. Maybe this will help

http://wiki.mikrotik.com/wiki/User_Manager/MAC_binding

Or, a semi-automated option, where you will need to collect the MAC somehow beforehand

http://forum.mikrotik.com/t/ip-mac-binding-in-mikrotik-router/80254/1

Last but not the least, this article has something that you may find useful - the “Add ARP for Leases” feature, where you would be able to probably collect or restrict the list later

https://rbgeek.wordpress.com/2013/01/02/configure-mikrotik-dhcp-to-assign-ip-address-to-only-authorized-clients-2nd-method/

Please post your findings here