I think asking for new crew at 20000 is too much. But now that Guinan is retired from the Gauntlet, her status is very similar to Locutus. The possibility of a choice between two hard to get crew might add motiviation for some. I have a 5/5 Loc, and thus completing 9000 more gauntlet rounds has little appeal.
Comments
Since Locutus and Guinan are from TNG and The Caretaker is from VOY, I suggest a new Cultural Figure from VOY, like:
5* Quinn
DIP
Q,Human,Maverick,Cultural Figure,Inspiring,Desperate,Philosopher