how to rewrite and replicate accounting?

I want to take all accounting packets received and either rewrite received attributes or append new attributes using a custom dictionary and then replicate the rewritten packets to multiple radius servers. Freeradius documentation seems to indicate this should be doable, but I can't seem to find any specific examples. Looks like I need some combination of the rlm_attr_rewrite, rlm_preprocess, and rlm_proxy modules? Is this correct? Thanks in advance. -jc