This paper introduces a more complete and complex dynamics simulation tool for an exoskeletal human upper limb assistant system. This heterogeneous simulation model couples the articulated dynamics of a 6 degree-of-freedom (DoF) wearable exoskeleton with an upper-limb human neu-romechanics model of 12 skeletal and 42 muscular DoFs with corresponding controls. Furthermore, the process forces of toolmediated manipulation tasks can be fed into the overall system. This simulation tool can be used for various purposes such as 1) design and evaluation of human-centered exoskeleton controllers 2) evaluating human motor control hypotheses during exoskeleton use and 3) investigating various properties and the performance on exoskeleton systems and manipulation tasks. This framework is used exemplary in designing and implementing a human kinematic latent-space controller for a power drilling manipulation task under exoskeletal assistance.