This keeps being suggested so here’s a TLDR on the issue:
Firstly I don’t know the specifics of the aircraft involved in this case but most crew rest areas are jammed into what is effectively the attic, between the top of the passenger cabin and the aircraft upper fuselage skin…they can be very tight on space, very low head room and most importantly usually accessed by a very steep, narrow set of stairs - bit like a loft ladder. It’s enough of a hassle getting into them when able bodied, I think you’d struggle to lift an inert body up into the space.
Secondly there are usually only enough bunks installed for half the normal crew complement, so half the crew go on break at one time and there maybe no spare bunks available to put the deceased.
Thirdly - I don’t know Qatars regs but horizontal crew rest isn’t a “nice to have” on ultra longhaul routes, it’s often a legal requirement on Long Haul sectors to have “ at least x hours in disturbed rest” (where x is often 3 hours or more) to allow the sector to be rostered at all.
If mid flight you start putting lights on and blundering around the rest area trying find somewhere to lay the deceased you compromise the sleep of those on rest and potentially compromise the ability to legally complete the sector.