This idea is for the capability to do external referencing of other FlexSim models in a parent model. This would be ideal for a production facility where there may be multiple production lines, or even a production line with multiple complex workstations. It's possible that those lines run fairly independently with a few defined connections. It would be useful to be able to create each line in a model by itself, and have the capability to combine them all into one model (without actually doing a merge).
When combining the models the feature would just create a reference to the production line model and could either duplicate it in a sandbox within the model on reset or run it in parallel in a separate instance (this would have its own difficulties). With this capability, if the child model changed, then it also be updated in the parent model.
It would also be necessary to allow for some overarching logic that would define the interactions between the individual models. I would imagine a process flow that allowed me to reference the events of the external model.
I see the functionality as similar to how AutoCAD does xrefs (yet admittedly, more complex).
This would make it much easier to maintain and build large models and leverage multiple people to create a large and complex model, as they could all be working on the models separately.