It would be very convenient and quick if the desired model state could be selected by a dropdown menu in the place part dialog. This wouldn't work if multiple parts were selected so then the option could be greyed out. All other times it would increase the workflow.
An alternative is to wait one step and allow the model state to be chose before the LMB places it in the assembly. This would allow the user to switch model states, inserting multiple of different states, as they are placing the parts.