Yes, I was thinking about suggesting it myself - having the bag especially for rubbish in the seatpockets. You see, in our airline we don't normally clean the cabin, leave alone toilets, ourselves. So I used to get annoyed with changing the sickbags, because pax were putting their rubbish in them.
Now, if we would have those "rubbishbags", it would be better and more convenient for all of us.
What a good idea!