Anything you do regarding the treasury carries a risk, and a big one at that - I can tell youth today, for instance, we killed 2 people robbing the treasury who had a tempest each, aswell as rifles and mags/equipment. Overall, it probably cost them each about 400k, give or take.
While I probably shouldn't suggest this, considering I'm a cop, the best way to get a safe yield from the treasury is through roleplaying a good story with the negotiation, who will hopefully then understand you and give you a deserved amount - remember, planting the bomb will mean lethals are authorised. This way is also better as, if you rob the gold, it is most likely that there will be a setup at the gold buyer too, so it's nigh on impossible that there is a chance of you selling any gold you get.
THat's just from my experience before being a cop, and if anyone asks, I never said anything