What exactly does this 人单合一的自主经营体 mean?
According to here, it should be 三是机制创新，要建立人单合一的自主经营体。.

机制创新 : innovation of mechanism/system
人 : staff/employee
单(订单) : order -> user needs
人单合一 : integrating order with personnel -> Every order is in the charge of one staff. Futher more integrating staff with user, make staff to achieve self-worth by creating value for users.
自主 : autonomous/independent/self-determination/self-leading
经营体 : operation unit
自主经营体 : (to make every staff one) independent operation unit

For whole sentence,
Thirdly, mechanism innovation, set up independent operation unit, which integrating order with personnel.

Reference: 人单合一双赢模式