IN A SITUATION WHERE WE OFFER A SEPARATE BENEFIT TO A SUBSET OF EMPLOYEES, WHAT HAPPENS?

You can create an SPD for that benefit only and distribute solely to the eligible/covered employees. If your objective is to have one ERISA Plan, you can include the separate SPD by reference in your Combined SPD/Plan Document. Alternatively, you could create a separate SPD/Plan Document for the separate benefit offered to the specific group of employees. The only drawback is that this establishes a second ERISA Plan, which if includes more than 100 participants, would require a separate 5500 filing.