I freely admit I may be wrong about this, but I don't believe anyone has ever done a story where Black Canary fights Poison Ivy. And that shocks me.
Think about it... They were both botanists by trade. They both started out in Gotham at about the same time and logically would have been going to the same college at the same time. So why not do a retcon where Dinah Lance and Pamela Isley went to college together and were close friends before Pamela went off to spend the summer interning for Dr. Jason Woodrue?
My original idea was to do this as sort of a one-off Times Past affair... but thinking on it, I can easily see using this as the basis for a Black Canary: Year One storyline. A young Poison Ivy would certainly be a worthy enemy for a young Black Canary. And I also think it would be fun to show Dinah having to butt-heads with a certain Dark Knight in her costumed identity even as Bruce Wayne starts coming to Dinah Lance - flirting, at first, but then asking questions that seem oddly relevant to the plant-based crimes Black Canary is investigating...
It has everything - The conflict as Dinah finds out a good friend has become something more than human and a bitter enemy. The romance between Dinah and Bruce as Dinah figures out his secret long before Bruce has any inkling that Gotham's new blonde vigilante is that quiet brunette girl who works at the flower shop. And a lot of butt-kicking, plant-wrangling fun.
And yes, I am going to see if Bruce Timm would be free to draw it.