schema map attribute from policy

Need to schema map from policy, have attribute names in eDir space, but query towards target system should be initiated from ITP (tail end of subscriber process).

Was sure that this was either an enhancement request or actually added somewhere. Was it in the JARs shipped with REST shim? (not using that shim.. but seem to recall something there).

Anyone got ideas?
Happy to also inject some sort of event that goes further into