I think the OP made the mistake of treating the DDF as a single object, so from this perpective i cannot agree wholly with the sentiment to "reopen" it. There are some good ideas in there, some of which might still be on the cards for all we know. I just wish people would stop referring to the DDF as some sort of holy grail.
My main concern is that FD keeps adding to the game in ways that provide new and interesting things to do, whether they came from the DDF or not. So far they generally speaking have from my perspective.
1.1 Community Goals - nice idea, and we have had some good ones. Recently we have been getting more lemons, so feel FD could pick up their game more here, but the general idea is good.
1.2 Wings - can't see any reason for anyone to complain about this. Nice feature and really adds to the game.
1.3 Powerplay - personally i think it was a great idea, just badly executed (doesn't stop me participating, i'm just hoping for improvements over time). If they made the powers linked better to the factions, made each power more unique in terms of what gave you merits, and you'd get merits for doing a variety of things for your power (major example, killing enemy powers in your own territories), i think powerplay could start to shine.
Not to mention all the other things they have added or changed since release. I was particuarly happy with the new limpet controllers and stuff that came with 1.3. Thanks to those we now have the Fuel Rats operating rescue services and mining is a lot easier and more fun.
CQC, while it came out of left field like PP, its also a nice feature, enabling those who just want a quick pew-pew to get it whenever they want, sure, it won't be for everyone, but there again, most things aren't.
Bottom line, will it be nice if FD pick up on some of the things from the DDF in the nearest future? Sure, many things there that would be a nice addition. Is it necessary? Hell no. As long as they keep adding new good stuff.