These boxes are plenty smart enough to do it.
First you'd need a prioritized unified series link list. That way you could add a show from any dvr to the networked dvr collection. When the units boot, first available becomes the 'scheduling master'. When the unit does its to-do list, it'd spread the shows to the dvr with the first available tuner and highest available free space on a rotational basis.
Then you'd have your unified playlist like we have now.
Then I think all you'd need is the ability to create custom folders and when creating a series link or an individual recording, you'd have a drop down that would let you pick which folder it went into.
Then you could 'sort' the recordings by 'his and hers', 'movies, sitcoms, kids shows', etc.
The collaborative scheduling part is 1980's technology. Organizing it better is 1970's tech.