Very simple.
Customize & create another MRGL for remote sites if you want to use Unicast MoH for them as well.
But, you need to take care of extra BW considerations for number of unicast MoH streams & need to size accordingly.
If possible, Mulicast MoH is recommended for Remote sites.
The following link will help you.
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/4_1_2/ccmfeat/fsmoh.html#wp1027465
Regards...
-Ashok.
With best regards...
Ashok