Seeing as he will being using his story (whats left) in the manga are some of the parts going to be flashbacks explaining more on the backround of the characters like why was Yoshi skin blue or the Taisou* and Alberto rivalry? Will the manga as well maybe start off where the OVA ended?
I think Carter found out that the new manga takes place in a parallel/alternate world or something. Because there are already some storyline differences from the OVA series, although it uses the same characters.
But, I'm thinking Imagawa might use some of his leftover ideas too. But I dunno.
As for the Taisou/Alberto rivalry as far as the OVA is concerned (it will be different in the new manga though, because of a major storyline change in the early chapters), here's what the liner notes say:
! > He has always wanted to defeat Taisou with his own hands after Taisou destroyed his best friend Cervantes and his right eye during the "Domino Operation"
! and later Imagawa said:
! > if an opportunity arises to make more episodes, I'll be able to show you the "Domino Operation"
! So, that's still really all we know about it. Except the liner notes tell the name of the storyline where it happened.
! Oh, and some people mistakenly think Cervantes died in that one flashback in the OVA, but he survived to later be killed by Taisou.
Oh, and here were the names of the other planned storylines:
"The Birth of Zangetsu the Midday"
"The Plan to Assassinate Daisaku - the Canary Penitentiary"
"The Boy of Three Days"
"The Greatest Battle in History - Kanshin vs. Koumei"
"The Boy Detective, Kindaiichi Shoutarou, Appears!"
"The Siege of Babel."
Also, there's "The Domino Operation" but I'm not sure where it takes place.
Oh, but if I'm not mistaken, "The Night Earth Stood Still" (the 7 episodes that were made) would take place right before "The Siege of Babel" (which sounds like the final battle).