I support the idea that LCC LH should work, but careful consideration has to be given to the numbers of available consumers.
In the SH LCC model, many people fly on short breaks etc that would not have done so if low cost carriers did not exist. Many that already went abroad began to travel more often with LCCs.
If there is a finite number of "ad hoc" passengers, then offering a long haul service would compete for its passengers with the existing LCCs short haul routes as well as schedule/charter airlines on the long haul routes.
Whilst I would welcome the availability, it may not actually put additional aircraft in the sky.