Regarding azimuth (direction) data on Mode C targets.
My training manual for the Honeywell TCAS states,
"The TCAS traffic display on the VSI is not considered accurate enough to support horizontal manoeuvres".
In practice the one visually acquired proved not to be the conflict on receipt of a TA or RA.
This is probably why flarm are not interested in info from old mode A/C transponders.