Heh, the fox guarding the hen house? To add to your thought, the questions themselves should not be picked by journalists either. You've heard some of the leftist slanted foolishness that's come out of that, huh? Maybe the participants should pick each other's questions. THAT might be a hoot.
FGS
Just give the participants a chess timer to control the equal time of the microphone, and let them have at it. Because the journalists' questions are inevitably influenced by the journalists' perspective, which is the same as the perspective of the Democrat.I even argue that the debates should be done on radio, and done over the the telephone so that they impose minimum constraints on the campaigning of the candidates. That way the debates could be frequent, and long - putting less pressure on the candidate with a settled philosophy, and gradually destroying the candidate who has things to hide.
Of course the candidate with something to hide ain't gonna go for that format (and that will never be the Republican, because the journalists would go for the jugular anyway). But perhaps that is the ideal format for the primary election; if you aren't the frontrunner and need the exposure you could do a debate with a similarly situated candidate in the other party - a win-win situation for ideologically based candidates.
Maybe that would have been the way for Reagan to have campaigned for the 1976 Republican nomination, for example. But then, usually one party has an heir-apparent. That's not the case for '08, unless Hillary walks away with it - and maybe my proposal would be the main chance of the Democratic governor who wants to keep her from doing that.