Interesting. But not an entirely new idea, Air NZ did introduce space plus seats on the A320's a little while ago, for elites. Same seats I believe, but with 35" seat pitch instead of 31-33" pitch in the rest of the plane. This idea seems to be the more or less the same as that.
As usual, DJ gets met with with a certain degree of mockery and derision for an idea that may or may not come to fruition. I think sold as a separate class, it may not work that well, but does have merit for allocation to elites and those travelling on higher economy fares.
I think one failing of DJ at the moment is really to grab market share on transcontinental services, hasn't been a lot of change in frequencies over the last few years in that regard. This idea may help, but to wander OT a little, will they ever contemplate widebodies or J class for that market?