Hi BenSa,
I'm confused. You wrote the BS4 is in option 6. This would mean it is een local Audio ML device and the BS9000 would be the Audio Master.
For the discussion I assume the BS9000, the BS4 and the BL3500 are all in different rooms.
In this setup the Command Link A.Mem can not start anyone of the devices in any room, The Command A.Mem in the BS4 room would start the BS4. The Command LINK CD in the BS4 room would in this system start the BS9000 and a Command CD the BL35000 in that room.
If........
......as an alternative the BS4 is the Audio Master (option 1 or 2) and the BS9000 a local Audio ML device in option 6. The Command A.Mem would start the BS4 and the Command Link A.Mem in the BS9000 room would start the A,Mem source of the BS4 on the BS9000. The BL3500 room should join with a simple A.Mem Command in that room. In this setup the Command Link CD in the BS9000 room would start the CD source of the BS4.
Note you can only distribute sources of the Audio Master or the sound of the Video Master through ML
Maybe an idea: discibe your system more detailed (where places, options etc)