I did somethig similar many years ago with an Avant
and the result was the same as yours.

Without an AV9000 TV/Center the AV works only as a ML source. 

But there are some conditions to fulfill and severe limitations:

1) use today's 9-conductor, the old 16-conductor ML cable used with the early AV9000s may cause troubles. Maybe the B&O Service has to solder a "jumper" between 2 of the pins of the ML socket to get the unit "9-conductor ML ready" - ask them

2) you have to use an one way remote like Beo4/BL1000 - get an older one with the "AV" button insted of "DVD"

3) forget about manual operation exept "Magic Open" of the doors and "Load" for CDs 

4) even with TV in option 2 the TV will not power on  by any audio command , you will have to start the TV by a video command like "TV" then "AV" plus "CD" or any audio command.

5) make sure that all reqired setup (re-programming of radio stations, clearing of timers, ...) is done while the MPAV beeing connected to the AV 9000 - no chance later on

PS: The proof of the pudding is in the eating - I connected my vintage "9-conductor ML ready" MPAV to my BV 7-55 and ... it worked  in the manner described ...