Uhh...yeah, I don't know about the manga being refered to but I do agree that multiple fics with the same main character can work. I mean, as long as the whole plot is so distanced from the original that it wouldn't be plausible to have them in the same fic then I don't see why not. I'm sure that the people who enjoyed the first fic with this character of yours (Mind you, post a link to that fic if you decide to do this follow-up thing, 'cause I wanna' see. :O) would love to see the character they already 'know' pop up again and how she has developed. The reason Ash is so boring because he doesn't develop (Hundreds of episodes and the only change he has gone through is a sudden leap from slightly comical dimwit with a dream to flawless Gary-stu, sheez...<_<); there are certainly many successful series of books centered around the same character(s). The important thing is that the character is well thought-out and multi-faceted and that the plots don't fall into a routine.
Basically, I'm saying go for it. ^-^