Concerning the 4-player format, you may recall, as Ken Jennings was nearing the end of his 75-game run on the show, that as a quasi-gag, I picked up on a suggestion in a news story for a "Ken Jennings Road Kill Tournament" and came up with just such a thing in which the 148 players he defeated over the course of his 74 Jeopardy wins would be brought back to play in a tournament of their own.
The format for my proposed "tournament" would have required 4-player games throughout its duration, with the first round of play reducing the starting field of 148 players to 37 game-winners, to which would be added the top 27 scorers from the non-winners to create a second-round field of 64. That field would have then be reduced to 16 semi-finalists, and then to 4 finalists in the next two rounds of tournament play, with the four finalists competing in a three-day total-point playoff to determine the eventual tournament winner. (And the whole package would have fit nicely into a 12-week, 60-program run.)
But I do detect a problem using 4-player play in regular Jeopardy games: Since, under the program's current prize structure, only the game winners get to keep the money they accumulate over the course of their play, the tendency would be to reduce the amount of money a daily winner would receive as a prize, since the total player score for a game would be spread among four players, rather than the current three -- and lower player winnings over time may not go over well with the audience!
The Super Jeopardy tournament that the ABC-TV network aired during the summer of 1990 compensated for that by increasing the score values for the game clues (to 200-1000 in the first round of play, and to 500-2500 in the second round), and playing the games for points, rather than dollars.
Michael Brandenburg
(The lesson here: Keep the current three-player format for regular Jeopardy play, lest you end up as a future "Jump the Shark" notable.)