You can have many connections to the NAS using the RADIUS LEG. I dont think there is a limitaion of how many NAS you can use but how will you seperate the subsciber attributes. Mostly I have seen CU using 1 NAS and using the username to seperate the fileds :
[Radius.NAS.SMX]
domain =cisco.edu
IP_address =x.x.x.x
NAS_identifier =smart222
secret =ciscosce
# This section defines the RADIUS attribute on which subscriber ID association is
# based. Default association is based on the 'user name' attribute. Uncomment this
# section if you want to base subscriber ID association on a different attribute.
[Radius.Subscriber ID]
# Radius protocol fields name.
# for multiple fields, use commas between the field name.
# field name shall not start or end with space bar, name shall not contain "=" char.
# Note - it is mandatory to create [Radius.Field.] section for each
# field defined in fields property
# (default: user_name)
# fields= ,,
fields=User_Name