not going to work.. even if a module were used to set +r on users..
+r means registered user and if anope detects such a user, but can't find any records of said users in its database of registered users, it will remove the +r as +r is the basis upon which anope decides whether a user is registered.. this is core functionality that modules wouldn't be able to bypass.
Even if that could be bypassed by not informing the core, the concept is also fundamentally flawed: assume a "guest" connects to the network and gets usermode +r, then changes nick to a registered nickname which he doesn't own.. anope sees +r and thinks the user has already id'd and said user is now considered identified for the nick.. so basically you are inviting nick stealing.