That would be a fun assignment

But, "M" has pretty meaningful [and powerful] lyrics. I know a lot of people on the forum like the lyrics, right?
But some personal favorites for me are:
TO BE
no more words
Dearest [My favorite Ayumi song of all time]
HANABI
HANABI ~episode II~
Memorial address ~take 2 version~
forgiveness
In The Corner
Moments
Will
However, lyrics that would be more poetic and please others more would probably be:
Moments
M [as I said before]
forgiveness
HAPPY ENDING
Pride
If I were to choose one from the list above I would choose "HAPPY ENDING". That seems appropriate for such a project.
I hope I helped