Luke Walton would not have been a better option. He is an inferior defender and an inferior rebounder relative to Odom and an even worse matchup versus for a strong physical beast like Glen Davis. Luke Walton is an adequate matchup against limited perimeter orientated power forwards but he should never be pitted against a physical big like Davis.
DJ Mbenga isn't even an NBA caliber player. That is like Boston putting Patrick O'Bryant in the fourth quarter of a Finals game and expecting him to be a difference maker. Mbenga is a liability defensively + offensively + is a subpar rebounder. If the Lakers want to get Mbenga some minutes, the best way is to use him against Perkins because that is the matchup that he'll do best with (limited responsibilities defensively and allowed to stay around the rim defensively = won't hurt you as much as he will against others).
The Lakers best matchup on their bench (out of their low level backup bigs) against Glen Davis is Josh Powell. He is not as strong as Davis but he's a high energy player who can play solid physical basketball defensively + on the backboards + and is quick enough to cover BBD's jumper.
Never liked Ron Artest as a power forward. He regularly hurts his teams whenever he has played the position in the past ... but he would be a decent option here too. His lack of rebounding relative to the position/opponent is the major problem, that's what has killed his team in the past when he's played the four spot.
I'm not saying these were definitive answers. I'll give Walton a little more credit than you do. The way Odom was playing almost anyone would have been better. He has better movement than what Odom was showing. A better sense of how to run the offense as well. I'm not saying compared to Odom at his best but tonight? Almost anyone would have been better out there in the fourth. Mbenga has size he can use at least. Powell I think should have got some run there. Why not go to him?
Artest as power forward--no way. He would get abused. Granted he killed them as well with poor shot selection again tonight. Had a few good boards and good D for the most part but he continues to kill them on the offensive end.
And, again, Phil was in a tough spit without Bynum but he showed no adjustments when the team he had on the court, and the schemes he was using, continued to get abused. His stubbornness in refusing to call timeouts as well.