So here are several stories that fit those requirements, and which I think I have a plausible chance of finishing by July 10 of this year:
1. Five Things That Never Happened to Rex and Anna Lewis (And One That Still Might)
--This is a GI Joe: Rise of Cobra fic (yes, I know) that does exactly what it says on the tin. I currently have the first three sections written to the tune of 9,000 words, and a couple hundred each for parts four and five. Part six is only an outline and might end up unwritten depending on my mood after rewatching the movie to refresh my memory of the characters and plot (insofar as they exist). Would probably be 15,000-18,000 words when complete.
--A Star Trek: AOS fic centered entirely on original characters with a brief cameo from the Enterprise near the end. The crew of a Red Cross ship investigate a mysterious plague on a small and deliberately isolationst human colony, where they run into a bunch of cultural issues (the colonists are a religious splinter group with negative opinions about technology) but begin to make progress... and then an Orion slaver/pirate fleet arrives in the system. Oops. I have about 14,000 words written and am stalled in the middle of the space battle section. Would probably be 18,000-20,000 words when complete.
3. The Light in Your Eyes
--Also a Star Trek: AOS fic, this one following Spock through the immediate aftermath of the Narada incident up to the Enterprise leaving on its new mission. Mostly about Vulcans and mourning and stuff, with significant secondary roles for Uhura and Kirk. Currently at 9,500 words, would probably be 18,000-20,000 words when complete.
4. New Horizons
--Post-epilogue, DH-compliant Ginny/Harry/Draco. No, really. :) Basically, Ginny gets forcibly 'retired' from the Holyhead Harpies around the time Lily leaves Hogwarts, so Harry takes her on a consolation holiday to Greece. They run into Draco, who's giving himself a consolation holiday after his divorce, and things kind of spiral from there. Featuring a bunch of political arguments, a bit too much alcohol, and probably no explicit porn because I am more here for the midlife crisis and romcom aspects. I posted two sections on my journal in draft form ages ago, and part of the third chapter is written. About 3,500 words written, should come to maybe 8,000 when complete. (Or 10,000, depending on how much they argue before I can talk them into possibly inadvisable sex.)
5. The Courting Dance
--A Chronicles of Narnia fic dealing with Aravis and Cor's attempt to get married despite stiff political opposition. Each chapter features a different POV, and there is at least as much world-building as romance. Eight chapters currently written and posted, probably seven left to go. Currently 12,500 words, will be around 24,000 when complete.
6. A Change of Season
--Chronicles of Narnia fic, sequel to "Out of Season" and "To Every Thing There Is a Season." This one follows Ilgamuth Tarkaan and Shezan Tolkheera through the end and aftermath of HHB, as they attempt to navigate extreme personal and political upheavals. I only have about 650 words of this written and my outline is extremely vague, so the estimated final wordcount is mostly a wild guess, but... I'd say 30,000 minimum. I'm putting this on here mostly because it's a story that I intensely want to write at some point, but I've needed external deadline pressure to get through the other two main fics in this sequence so perhaps a similar kick will work on this one as well. It would require me to write at least twice as many words as any other option, though.
--A BtVS/Gundam Wing/Naruto crossover in which Faith Lehane, Duo Maxwell, and Uchiha Sasuke accidentally get yanked into a hell dimension and have to work together to get home. Along the way, they have some sex. :) This is post-Chosen for Faith, post-Endless Waltz for Duo, and in the third year of the timeskip for Sasuke; it ignores all BtVS comics, anything from Preventers Five, and pretty much all of post-timeskip Naruto. Nineteen chapters are currently posted, totalling roughly 44,000 words. I estimate another six to ten chapters before the plot wraps up. (I have a relatively firm outline, but I'm not always great at guessing how many words it will take to cover each point.) This should be roughly 60,000 words when complete, though only 16,000 or so would be new.
So. With that in mind, here is a poll:
Open to: Registered Users, detailed results viewable to: All, participants: 22
If Liz attempts the WIP Big Bang, which story should she finish?
"Five Things That Never Happened to Rex and Anna Lewis" (GI Joe: Rise of Cobra)
"Intervention" (Star Trek: AOS)
"The Light in Your Eyes" (Star Trek: AOS)
"New Horizons" (Harry Potter)
"The Courting Dance" (Chronicles of Narnia)
"A Change of Season" (Chronicles of Narnia)
"Lemonade" (BtVS/Gundam Wing/Naruto)
If you can't get the poll to work for you, please leave a comment instead!