It's an edited picture, not a real car. I guess someone handy with sheetmetal surgery and welding might be able to do that in real life as well?
The break's rear end is just a little longer than a sedan's. I've added a few centimeters behind the fuel filler flap. That means also the rear bumper must be longer.
As the sedan's reinforcing solid steel parcel shelf would no longer be present in a break, some sort of a compensating structure would have to be constructed instead. This would mean the slimmer than original C-posts would have to be quite strong, with maybe a tubular section under the roof connecting the tops of the new C-posts to give that area sideways strength.
Similarly, the tailgate surrounding would have to be strong. Maybe it could be adapted from some existing estate/stw? Tailgate lock&hinges placement, movement arcs and sealing issues would have to be dealt with, too.
Then finally we'd have to tie the C- and new D-posts together lengthways. For the roof, this could be done with a similar structure as in the existing roof between A-/B- and B-C-posts. As for the waistline, maybe a thick enough strip of sheetmetal running between C- and D-posts. Spotwelded from its top to the top edge of the rear quarte panel, creating a flange for the rear side window seal?
For someone handy, that might not be too difficult. More difficult would be various minor details like making a mould for rear and rear side windows, their seals, tailgate construction and its movement plus correct palcing of support struts etc etc. Then, depending on country, trying to convince the local authorities that the conversion is safe and approvable for road.
But, like you, I also would like very much to see my vision become reality!
