forward authentication, but take reply attributes from local db

Hello! Lets say i have primary radius server with users in file. And i also have secondary one, with the same users (logins and passwords are the same). How do i forward/proxy access-request from primary to secondary and in case it sends back access-accept to primary - it takes user attributes from local database (of primary). No just return to NAS what secondary gave me, but rewrite it according to local config. The main goal of secondary - just either accept or reject user. is it even possible?