As already mentioned NZ has been doing this for some time. The "Skycouch". To be done properly the seats have to be different...they have to have the other "seat pan" built in (that swings up and turns the whole surface between rows into a flat (short) bed. The new LH "Sleeper seats" in that photo appear to have that feature, whereas the current "Sleeper Row" does not. They are two different concepts, right? (The LH photo does not show such a feature in the other rows pictured either)

On NZ it is about 6 rows per aircraft..I think. NZ also provides clever seat belt arrangements for when you are lying down, and lots of bedding. Flew LAX-AKL recently in the "Skycouch"..by myself. For about the same price as Premium Economy I got to lie down... brilliant. Yes, you need to lie with knees bent... and the rest of the experience is still Economy... but I suspect LH will find those proper sleeper seats a reasonable investment, as I'm sure NZ has. If not sold as "Sleepers" of course the seats can still be sold.."normally".