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If your load is not predicted to increase A LOT in the foreseeable future, get one CCR1016-12S-1S+ with the SFP modules and see how it goes.
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I don’t mind getting a cheap CCR 
1U server with additional NICs and RouterOS?
Is it possible to aggregate your connections on a switch, then 2x10gbit LACP to ccr1072 by VLAN?
Though you may not like the power consumption.
According to Mikrotik documentation, You can:
https://wiki.mikrotik.com/wiki/MikroTik_SFP_module_compatibility_table#SFP.2B_interface_compatibility_settings_with_1G_links
https://wiki.mikrotik.com/wiki/MikroTik_SFP_module_compatibility_table
It’s not so small. Pure math:
CCR1009 has 9 cores 1GHz = 9GHz
CCR1016 has 16 cores 1.2GHz = 19,2GHz
(19,2 - 9) / 9 = 113% more.
What is consuming your CPU? Depending on the task of those routers, you can sometimes optimize firewall rules, decide
between connection tracking or not, queuing can also be done in different ways, and when you traffic increases you may
be able to have multiple CCR1009 alongside handling part of the traffic.
Also, instead of having a central place where
- all traffic has to pass
- all the firewalling has to take place
- all the queues have to be implemented
you may be able to have these tasks in different routers.
E.g. it does not seem to be a good idea to do the BGP (I presume internet routing, not BGP for your local network) on the
same router were you also do firewalling and queueing individually for customers.