Model for appraisals for a new 3 way co-leadership team in an organisation which is actively handing over centralised power

I’m looking for a policy which incorporates a move toward flat hierarchy and increased community control.

My group/organisation focuses on community asset development (Social Housing, Work Spaces, Co-working, Youth Club, Public Living Room and Community Tech Hub. We have a membership-based structure. We have 880 active members and/or staff. Our members/staff are based in and around Hastings. Our annual turnover is 300k-500k.