If you stop a host instance all currently active orchestrations are persisted to the MessageBox. Dehydrated and suspended orchestrations are already persisted. On restart all persisted orchestrations are evaluated to see if they should be made active again.
The only problem you may have is if your orchestrations are in the same assembly or have some dependencies that require you to remove both Orch1 and Orch2 assemblies. In order to remove an assembly you must terminate all orchestrations that are currently using that assembly.