I wonder if the reason we don't see more of that approach is network sensitivity to criticism over alleged bias/imbalance.

I doubt that very much, I think most of these sorts of decisions are all about ratings.

The PBS-style or old-network-news style of moderation and news analysis never brought in more eyeballs than a small portion of the public interested in that sort of thing. The conflict and drama of political adversaries brings in many more eyeballs.

"Crossfire!" as Bob Novak used to shout at the beginning of that pioneering show (pioneering of the profit model, I mean,) is assured to attract a lot more viewers. If you're an outfit running for profit, you've got to have some.

And it also helps a great deal to add some "characters" with "personality" that are good/evil or at least interesting in the viewers' eyes. Moderates are boring. Highly adversarial political debate way outdraws analysis as far as "must see" or "must participate." If a show is single-character based, like Limbaugh, Maddow, or Sharpton, it has to constantly return to the topic of "what the enemy is saying/doing" to keep the eyeballs.

I often see "holier than thou" comments in the blogosphere when this whole thing is brought up. I don't take them seriously at all. Many more people participate and are excited by politically adversarial points than by analysis or wonkery in the blogosphere, too. The more adversarial, the bigger the audience, and the more character driven, the bigger the audience, the more emotional, the bigger the audience.

Here's just a few examples that come quickly to mind:  Look right now on Dagblog and see how Resistance's comments on guns increase hits and participation. Who would begrudge Richard Day's long constant jihad against conservative pundits and wingnuts who drive him mad? Look at how participation drops when there is no main boxing event like an election or a big emotional news event like the Newtown shooting. Everyone has an opinion in the latter case, and everyone is a mightly big market share. Back when TPMCafe got intentionally flooded by Obama fans by the management, and one could not talk about anything else but the primary fight because any attempt to scrolled away, I remember Andrew Golis being frustrated by the success of it, doing a post screaming "enough now, can somebody anybody post about something else besides Hillary Clinton?"

I don't think that this should necessarily be denigrated because I think many more people's brains work this way: they need adversarial debate to get their thought juices working. I am not one of those people, but I think I am in the minority. (Not to mention, in this country, we have a two-party, not a parliamentary system, but that's another whole ball of wax.) So running politics and news shows and blogs "for profit" as it were really is running them in a sort of "majority rules" way. I don't think we can ever go back to elites running news shows not-for-profit, elites deciding what you should think about "for your own good" like a class in school, where the result is: many people tuning out all together.  I just wish I would see more of the promised "boutique" marketing for those of us who don't like what the majority likes and not end up pandering to hits.

P.S. The movie "Network" basically laid this all out long ago, always worth a re-watch. And Kucinich's job at Fox is to be an interesting "character." If he's just a dweeb like Colmes, it's a fail.