You can always ask for what you want if the purser comes for giving the talk. I have only been refused once for what I had asked for and I am only a lowly gold.
I only request stuff from just one class above.. I usually ask for the F slippers when I am in J. They usually give it in a duty free bag to be discreet. F champagne in J is also possible (was politely refused by the purser once.I am not a big fan of Dom 2003 anyway ).Asking for stuff from the F cabin when flying Y would be a bit OTT.