[Galadriel55]

I have a feeling that Glorfindel would have gone, out of a sense of duty, if the two last open slots of the Fellowship would not have been filled by Merry and Pippin. As for going as a guard, even if you're going half-way you're still going. If yu add one guard, you may as well add two, and three, and the point of 9 members is gone. Also, they did not know for sure they would pass through Lorien. Beyond that they had to start out going south, they had no clue what their route will be. They had to improvise on the spot depending on the situation. Giving them a guard until a certain point defeats this point also. And if you don't give the guard a destination up to which he must protect the Fellowship, I doubt anyone would just say mid-way that his job is done and he will return home. He'd follow till the end, which would just make it 10 members. 9 is a good number - not too big, not too small, and it reflects the number of the Nazgul. If you stray to either direction you may as well forget the whole idea altogether.