If i use hq uplink on 3 rebel veterans witch in turn give orders to the 3 turrets do all six become immune to panic in addition to the 3 units i give orders to?

Looks legit. Very exensive and probably not very efficient, but legit.

Why not just give the three trooper order to the veterans that lands 6 orders on your Corp units. Another thing is that the emplacments are less likely to be panicking and a cheaper option would be to issue 1 order to a rebel veteran, use comms relay on your emplacements to chain the commands to the other two rebel Veteran units , giving you 4 order tokens one 3 Rebel Veterans 1 on a mk2 medium blaster emplacement and another two orders to give out. Only 10 pts on upgrades instead of 57 for rebel comms troopers and HQ uplinks, you can do this every turn you can spare an order for a single veteran unit.