To my knowledge, that's not possible.
Hmm, the what's new hub normally opens by default when you click the standard people hub tile, at least it does on my 920, but bear in mind if you back out of the peoples hub in the contacts list it will reopen in the contacts list the next time you click the peoples hub tile
Yes, does the same on my Lumia 920. Just thought if there was an app or way to have as a live feed tile showing a certain number of posts from FB and twitter.
You could do that with your 25 closest friends. Just add them all to a Group and you'd get a Live Tile showing their most recent updates and could click in to see them all. I say "25" because I think I heard that is the limit of people in a group.