Is sending out disbursement authorizations for employee travel allowances considered cooperation in sin and aggression, due to the uncontrolled mixing in mission and training locations?

Your work in sending disbursement permits is not a sin, because it is for a permissible act, and it is not cooperation in the sin of prohibited mixing. The sin lies in the mixing itself, not in the training. It is not permissible to remain in an unregulated mixed work environment for someone who falls into sins because of it and fears temptation for himself.