well, first, it's a proposal - it doesn't exist. The research around something of this sort is only just beginning (according to the article), so "they" don't even know if it will work. It's all theory.
I would need a very good explanation of how a hologram (because that is what we're talking about), would take on physical characteristics, even if we're talking about nanites somehow bonding together to form a larger figure.
How does each nanite interact with the thousands of others? Where's the interface? Where does the charge/powersource come from? If it's not tethered to a power source, are there internal capacitors at work?
What will be used for commands? A CPU that sends it's wireless signal to each nanite? What about degradation?
Just a lot of unaswered questions. Theories, yes. Concrete answers? Not yet.
But it reads well and looks good on paper. And I'm certainly aware that there's technology that is as yet discovered that will amaze us, and this could be it. I ride around in my pickup with all it's gadgetry and CD changer and gauges and lights and electronic seats, electric windows, variable cam timing etc etc and I think, this truck is 'normal.' look at an F100 even 50 short years ago - 1958. This thing would be science fiction in comparison - and 50 more years to 1908? Those folks wouldn't even be able to begin to comprehend what it is, and the power it has, the speed that it can go and the things it does. It'd be a spaceship.
SO, this DPR may actually be something.
we'll see...