Just going with the team you're currently using, I'd say keep Mature up front... Not only can she build a good amount of meter if you're "moving" with her properly via rushdowns, pokes, qcb+B, crossups, etc, she can do great damage with little meter. Of course every character is more effective with meter, but the beauty is she doesn't heavily rely on it like the rest of the team... Again, you have to be constantly rushing down, and doing multiple things if you want build meter rather quickly. She's very capable of building back whatever meter she spent just as fast imo...
Leona needs the most, but builds the least, and Shen is good enough to be in the middle imo, even though he can use the whole thing... I don't see many Leona players building a bunch of meter, but I'd say if you did have her at point, she'd have to do alot more than Mature would...
As far as other battery characters go, the first one that I can easily think of is Mai... The only downside to her is that she kinda has to burn some meter to do some decent damage, because most are trying to do her Neomax or some HD combo into Neomax (correct me if I'm wrong). Kula might be decent in the meter building, since she has that s.A glitch, and her "autodrive" playstyle from '99 seems to still be good in damage dealing and meter building... Yeah K' is great too...
Also, depending on how effective you are in movement, Billy can also build good meter... Meterless corner combos ending in Senpuukon and cr.C as well as using his f+A and cr.B can help build meter quickly...