I'd desert all my other fandom pairs for a good Dahlia/Cara happy ending fic. The show made me root so hard for those two; then all the wtfery with true love Leo pissed me off and made me root harder. :p Fandom would be so lucky for you to correct this injustice. Although before getting too deep into something lengthy, you might want to wait for the finale to air. I know the fic you described would be AU (well unless the producers have access to your brain), but there is a slim to nil chance Dahlia may make it out alive... or she may die (again) in really sucky fashion with no further interaction with Cara or closure on their relationship pissing you off and effectively killing any and all inspiration. :(

But more fic, please. lol.