I can appreciate that life becomes more complicated and as we get older most of us have less and less time to spend on video games. I am not entirely against the idea of a middle ground but I am absolutely against casualization for the sake of the lowest common denominator.
(Also just more going to cite the FFXIV or FFXI-2 poll thread in which there is a living portion, of which I mean majority, of players here and now who want much harder world but I digress.)
The ability to solo the entire campaign is not 'Middle Ground"
The ability to PL to 40 is not "Middle Ground"
The only hint of difficult content is found in end game is not "Middle Ground"
We already have leves for those without a great deal of time on their hands but wish to progress. One should not be able to progress faster solo then leves or a solo class which I hope they introduce. To give time poor players to opportunity to make their own way without watering down the experience for the rest of us. Story Line quests should be 2 parts solo/fetch/NM hunt 1 part group fight that requires a great deal of effort. I don't want to force everyone to be in a PT constantly to get any of the Story but it should be segments of pure story following a difficult challenge which you MUST band together.
By hitting key points where players will all be stuck you collect pools of available Pt members at junctures that are easy to /shout for. 6-2 being a good example. Even the most casual players and those with short play time per day can commit to a half a dozen real fights. It may take them more them a week but hey, thems the shots. If you can't put in more effort don't expect to move through as fast.