If you are actually writing something properly, then the characters should develop on their own though, right? So it's natural that you wouldn't know how the manga would end when you begin it. If you did, there'd be no point in writing it at all and nobody would read it...
In any case. I have a complicated view of Eijun. I want him to be the ace, but I also want to hit him very very often. Every time he goes off on one of his silly yelling fits about one of the other players - "become a man, Harucchi", "Now you have to live up to being a captain!" "THis is the level of this guy right now"...etc. ALL OF THOSE yelling moments make me really want him to go away and never come out again.
And that's for me the weakness in the writing of his character because in every other respect he's really likeable. He's honest, direct, works hard, plucky, fights back against adversity, deals with criticism, works to improve his game, and never gives up. If only he'd stop shouting stuff that's not funny the first time, let alone a million times later - I'd absolutely have him in my top 5 characters.
But that makes that impossible.
So Furuya. I don't understand the Furuya hate. To develop Eijun requires developing Furuya. While wanting Eijun to be the ultimate ace, I have a lot more affection as time has gone on for Furuya (not just because he doesn't shout stupid stuff all the time) because there's this sweet innocent simple side to him whereby he is just happy to be playing in a team. And I think it's fine to develop both of them, so they both grow. I think the series is stronger for having both of them. And if Eijun would just stop yelling stupid stuff all the time, I'd enjoy their rivalry so much more.
...But my #1 is Miyuki, and so what I want to see is the ultimate Koushien final win in THIS year, with him as catcher. I feel like if the series doesn't build on that very first episode, (and continued hints in that direction) where Eijun basically changed the course of his life having met Miyuki, then it will be a wasted trajectory. I am fine with Eijun taking time to get to the ace point, because I like character development and I'm patient. But I don't have any interest in the new catchers or a team without Miyuki or, frankly speaking, Kuramochi, who is probably my #2 character.
So however this arc twists and turns towards the finale, I want to see the ace/catcher pairing of Eijun and Miyuki winning at Koushien as the culmination of the plot.
How it gets there I really don't mind. So long as Eijun stops yelling stupid. I don't blame Haruichi for getting annoyed with him. I would have hit him by now.
Also!
I feel bad for Kawakami. :)