Steve Lightle would be my first choice,but I doubt he would be able to put out a monthly book,due to his record on the Legion and Doom Patrol.
Gene Gonzales is a huge Legion fan,it would be neat to have someone draw the Legion that is as passionate about them as Paul.
But like you I can't recall him on a monthly book,though I do like his art.
http://genegonzales.blogspot.com/ Giffen may work as a co-plotter and breakdown artist(it would be a good way to help keep the book on time),but alot of Legion fans have a love/hate feeling towards him on the Legion,myself included?
Alan Davis would be a big draw,and has proved he can do a monthly,but the Legion isn't your run of the mill monthly!
Another artist that reminds me of him in style is Paul Pellitier,if they could get the two of them to alternate on the book,with Mark Farmer on inks.
Other past Legion artists would be welcome for an issue or two like,Grell,Sherman,Starlin and Jurgens.
As for the newer artists,I'm not up on my artists like I used to be,I know the guys who worked on the Legion like Manupal and Copiel,but don't buy enough books anymore to keep up with the rest,though the Green Lantern artists look pretty darn good.