I've been thinking since the Blu-rays were announced it would be good to have both parts on one disc, this is probably the 2nd best way of doing it.
The other would be to have all of part 1 repeated on the season 4.1 disc.
Of course with the Blu-Ray capacity there's no reason they couldn't have feature length and episodic version on the same disc, but I don't think this will happen.
Family belongs with it too really.
Still anyway, the Best Of Both Worlds gets the best of both worlds.