Hi,
To work on a 360-degree appraisal system, the appraisee has the appraisal form for SELF, Subordinate, Peer, Immediate Superior, HOD. Additionally, we can take appraisals from inter-departments with which that particular employee has regular transactions. As you mentioned it's a bank, the appraisee may deal with external customers like the public, so you can also include appraisals from the same.
Next, you design work-related KRAs' weightage and behavioral aspects weightage for rating purposes. Subsequently, you will get appraiser-wise weightage as well as the final outcome.
Manoj