Wouter,
There's nothing new about this method for an 'unstayed' rig. I was building a truly awful 12ft catamaran called a "Peanut" back in 1975 that used exactly that method for it's rig.

It had grp hulls with 'turrets' that supported a square ali tube frame, strung with a trampoline (similar to a H16) the side bars that supported the lower mast tube were through-bolted the tramp frame around where the shrouds would normally be.

The reason the boat was so awful was it was heavy for its' size and prone to nose dives. As a result it was slow and 'twitchy'.