Personally I want to say they added Lois kissing Lex on the lips to up the ick factor of the episode. OK. maybe I don't believe it, but it makes no sense. If she has decided she loves Clark, than kissing Lex on the lips is an act of disloyalty.
I didn't have a rehearsal dinner the night before I got married. We went out with my fiancées sister, and a close friend of her's and said friend's husband. So that part did not seem odd.
That lack of a maid of honor and best man I mainly chalk up to the same reason the wedding was at Lex Tower, low budget TV production. Also, having such people would add to the confusion.
At another level it is an early sigh that this is not the central focus wedding of the series. However, deep down I think everyone knows that somehow Clark will save Lois, Superman will escape, and she won't be left married to Luthor.
